Systems and methods for SSL session management in a cluster system

ABSTRACT

The present invention is directed towards systems and methods for managing one or more SSL sessions. A first node from a cluster of nodes intermediary between a client and a server may receive a first request from the client to use a first session established with the server. The first request may include a session identifier of the first session. The first node may determine that the first session is not identified in a cache of the first node. The first node may identify, via a hash table responsive to the determination, an owner node of the first session from the cluster using a key. The key may be determined based on the session identifier. The first node may send a second request to the identified owner node for session data of the first session. The session data may be for establishing a second session with the server.

RELATED APPLICATIONS

This application is a nonprovisional of, and claims priority to U.S.provisional application 61/809,318, filed Apr. 6, 2013, entitled“SYSTEMS AND METHODS FOR SSL SESSION MANAGEMENT IN A CLUSTER SYSTEM”,which is hereby incorporated by reference in its entirety for allpurposes.

FIELD OF THE DISCLOSURE

The present application generally relates to the management of securesockets layer (SSL) sessions. In particular, the present applicationrelates to systems and methods for SSL session management in a clustersystem.

BACKGROUND

Remote computing and centralized management of computing environmentshave converged to provide remote access to resources such as data andapplication resources, but also to incorporate management aspectsincluding multi-level security (e.g., authentication and firewallpolicies), support for a variety of access points and clientenvironments, and uniform presentation of resources. Systems, such asnetwork appliances that help to provision applications and/or data toremote users may deliver computing and/or application services in avariety of ways. For example, dedicated servers may provide access toparticular software applications by delivering application components toa remote client for execution. Network appliances may provide proxyfunctions such as secured session establishment. As application andcomputing needs evolve, such systems may have to provide a higher levelof service in both delivery and performance. Accordingly, some of thesesystems may provide increased levels of parallel processing ormulti-tasking by incorporating multiple hardware and software engines toprocess packets.

BRIEF SUMMARY

The present disclosure is directed towards methods and systems for SSLsession management in a cluster system. A device or appliance,intermediary between one or more client and servers, may include acluster system that comprises a group of nodes. Each of these nodes maycomprise a multi-core system and may host one or more processing enginesfor handling packets. The present disclosure provides methods andsystems to efficiently manage SSL sessions established across nodesand/or cores, including nodes having symmetric or asymmetricconfiguration. By interoperating between nodes within the clustersystem, the nodes can present a single node image to a user or deviceinterfacing with the appliance. These methods and systems can use adistributed hash table (DHT), that may allow any core receiving asession resume/reuse request, to identify an owner code of the requestedsession. The distributed hash table can receive as input a key derivedfrom a session identifier, to output information about the owner core.Copies of the distributed hash table may be available to each coreand/or node, and can be used to mark particular sessions that may beinvalid or non-resumable. Based on the identification of the owner core,the owner core may be requested to provide a response that includessession information for the requested data. The receiving core may thenestablish a local cloned session of the requested session, responsive tothe session resume/reuse request.

In one aspect, the disclosure is directed to a method for managing oneor more secure socket layer (SSL) sessions. The method may includereceiving, by a first node from a cluster of nodes intermediary betweena client and a server, a first request from the client to use a firstsession established with the server. The first request may include asession identifier of the first session. The first node may determinethat the first session is not identified in a cache of the first node.The first node may identify, via a hash table responsive to thedetermination, an owner node of the first session from the cluster ofnodes using a key. The key may be determined based on the sessionidentifier. The first node may send a second request to the identifiedowner node for session data of the first session. The session data maybe for establishing a second session with the server.

In some embodiments, the first node may receive a request to reuse,resume or clone the first session. The first node may receive therequest from the client as part of a handshaking process forestablishing a SSL session with the server. The first node may determinethat the first session is not identified in the cache based on thesession identifier of the first session. The first node may determinethat the first node is not the owner node of the first session. Thefirst node may determine generate the key based on at least one of thesession identifier or a unique identifier of an entity from which thefirst request is received. The first node may receive a response to thesecond request, the response indicating that the requested first sessionis invalid, expired or not resumable.

In certain embodiments, the first node may establish a new session ifthere is no response to the second request, or if a response to thesecond request does not include the requested session data. The firstnode may establish the second session if a response to the secondrequest includes the requested session data, the second sessioncomprising a session cloned from the first session. The first node maystore information about the second session in at least one of the hashtable or the cache of the first node.

In another aspect, the disclosure is directed to a system for managingone or more secure socket layer (SSL) sessions. The system may include acluster of nodes intermediary between a client and a server. A firstnode from the cluster of nodes may be configured to receive a firstrequest from the client to use a first session established with theserver. The first request may include a session identifier of the firstsession. The first node may be configured to determine whether the firstsession is identified in a cache of the first core. The first node maybe configured to identify, via a hash table responsive to thedetermination, an owner core of the first session using a key, the keydetermined based on the session identifier. The first node may beconfigured to send a second request to the identified owner core forsession data of the first session. The session data may be forestablishing a second session with the server.

In some embodiments, the first node is configured to receive a requestto reuse, resume or clone the first session. The first node may beconfigured to receive the request from the client as part of ahandshaking process for establishing a SSL session with the server. Thefirst node may be configured to determine whether the first session isidentified in the cache based on the session identifier of the firstsession. The first node may be configured to determine whether the firstnode is the owner node of the first session. The first node may beconfigured to generate the key based on at least one of the sessionidentifier or a unique identifier of an entity from which the firstrequest is received.

In certain embodiments, the first node is configured to receive aresponse to the second request, the response indicating that therequested first session is invalid, expired or not resumable. The firstnode may be configured to establish a new session if there is noresponse to the second request, or if a response to the second requestdoes not include the requested session data. The first node may beconfigured to establish the second session if a response to the secondrequest includes the requested session data, the second sessioncomprising a session cloned from the first session. The first node maybe configured to store information about the second session in at leastone of the hash table or the cache of the first node.

The details of various embodiments of the invention are set forth in theaccompanying drawings and the description below.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via an appliance;

FIG. 1B is a block diagram of an embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIG. 1C is a block diagram of another embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIG. 1D is a block diagram of another embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIGS. 1E-1H are block diagrams of embodiments of a computing device;

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server;

FIG. 2B is a block diagram of another embodiment of an appliance foroptimizing, accelerating, load-balancing and routing communicationsbetween a client and a server;

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server via the appliance;

FIG. 4A is a block diagram of an embodiment of a virtualizationenvironment;

FIG. 4B is a block diagram of another embodiment of a virtualizationenvironment;

FIG. 4C is a block diagram of an embodiment of a virtualized appliance;

FIG. 5A are block diagrams of embodiments of approaches to implementingparallelism in a multi-core network appliance;

FIG. 5B is a block diagram of an embodiment of a system utilizing amulti-core network application;

FIG. 5C is a block diagram of an embodiment of an aspect of a multi-corenetwork appliance;

FIG. 6 is a block diagram of an embodiment of a system utilizing amulti-core network application;

FIG. 7A-7B are flow diagrams of an embodiment of steps of a method formanaging session persistence and reuse in a multi-core system;

FIG. 8 is a block diagram of an embodiment of a cluster system;

FIG. 9A is a block diagram of an embodiment of a system for managing oneor more secure socket layer (SSL) sessions; and

FIG. 9B is a flow diagram of an embodiment of steps of a method managingone or more SSL sessions.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION

For purposes of reading the description of the various embodimentsbelow, the following descriptions of the sections of the specificationand their respective contents may be helpful:

-   -   Section A describes a network environment and computing        environment which may be useful for practicing embodiments        described herein;    -   Section B describes embodiments of systems and methods for        delivering a computing environment to a remote user;    -   Section C describes embodiments of systems and methods for        accelerating communications between a client and a server;    -   Section D describes embodiments of systems and methods for        virtualizing an application delivery controller;    -   Section E describes embodiments of systems and methods for        providing a multi-core architecture and environment;    -   Section F describes embodiments of systems and methods for        managing SSL session persistence and reuse in a multi-core        system;    -   Section G describes embodiments of systems and methods for        providing a clustered appliance architecture environment; and    -   Section H describes embodiments of systems and methods for        managing one or more secure socket layer (SSL) sessions.        A. Network and Computing Environment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environmentcomprises one or more clients 102 a-102 n (also generally referred to aslocal machine(s) 102, or client(s) 102) in communication with one ormore servers 106 a-106 n (also generally referred to as server(s) 106,or remote machine(s) 106) via one or more networks 104, 104′ (generallyreferred to as network 104). In some embodiments, a client 102communicates with a server 106 via an appliance 200.

Although FIG. 1A shows a network 104 and a network 104′ between theclients 102 and the servers 106, the clients 102 and the servers 106 maybe on the same network 104. The networks 104 and 104′ can be the sametype of network or different types of networks. The network 104 and/orthe network 104′ can be a local-area network (LAN), such as a companyIntranet, a metropolitan area network (MAN), or a wide area network(WAN), such as the Internet or the World Wide Web. In one embodiment,network 104′ may be a private network and network 104 may be a publicnetwork. In some embodiments, network 104 may be a private network andnetwork 104′ a public network. In another embodiment, networks 104 and104′ may both be private networks. In some embodiments, clients 102 maybe located at a branch office of a corporate enterprise communicatingvia a WAN connection over the network 104 to the servers 106 located ata corporate data center.

The network 104 and/or 104′ be any type and/or form of network and mayinclude any of the following: a point to point network, a broadcastnetwork, a wide area network, a local area network, a telecommunicationsnetwork, a data communication network, a computer network, an ATM(Asynchronous Transfer Mode) network, a SONET (Synchronous OpticalNetwork) network, a SDH (Synchronous Digital Hierarchy) network, awireless network and a wireline network. In some embodiments, thenetwork 104 may comprise a wireless link, such as an infrared channel orsatellite band. The topology of the network 104 and/or 104′ may be abus, star, or ring network topology. The network 104 and/or 104′ andnetwork topology may be of any such network or network topology as knownto those ordinarily skilled in the art capable of supporting theoperations described herein.

As shown in FIG. 1A, the appliance 200, which also may be referred to asan interface unit 200 or gateway 200, is shown between the networks 104and 104′. In some embodiments, the appliance 200 may be located onnetwork 104. For example, a branch office of a corporate enterprise maydeploy an appliance 200 at the branch office. In other embodiments, theappliance 200 may be located on network 104′. For example, an appliance200 may be located at a corporate data center. In yet anotherembodiment, a plurality of appliances 200 may be deployed on network104. In some embodiments, a plurality of appliances 200 may be deployedon network 104′. In one embodiment, a first appliance 200 communicateswith a second appliance 200′. In other embodiments, the appliance 200could be a part of any client 102 or server 106 on the same or differentnetwork 104,104′ as the client 102. One or more appliances 200 may belocated at any point in the network or network communications pathbetween a client 102 and a server 106.

In some embodiments, the appliance 200 comprises any of the networkdevices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,referred to as Citrix NetScaler devices. In other embodiments, theappliance 200 includes any of the product embodiments referred to asWebAccelerator and BigIP manufactured by F5 Networks, Inc. of Seattle,Wash. In another embodiment, the appliance 205 includes any of the DXacceleration device platforms and/or the SSL VPN series of devices, suchas SA 700, SA 2000, SA 4000, and SA 6000 devices manufactured by JuniperNetworks, Inc. of Sunnyvale, Calif. In yet another embodiment, theappliance 200 includes any application acceleration and/or securityrelated appliances and/or software manufactured by Cisco Systems, Inc.of San Jose, Calif., such as the Cisco ACE Application Control EngineModule service software and network modules, and Cisco AVS SeriesApplication Velocity System.

In one embodiment, the system may include multiple, logically-groupedservers 106. In these embodiments, the logical group of servers may bereferred to as a server farm 38. In some of these embodiments, theserves 106 may be geographically dispersed. In some cases, a farm 38 maybe administered as a single entity. In other embodiments, the serverfarm 38 comprises a plurality of server farms 38. In one embodiment, theserver farm executes one or more applications on behalf of one or moreclients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or medium-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The clients 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality for identifying and providing address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Referring now to FIG. 1B, an embodiment of a network environmentdeploying multiple appliances 200 is depicted. A first appliance 200 maybe deployed on a first network 104 and a second appliance 200′ on asecond network 104′. For example a corporate enterprise may deploy afirst appliance 200 at a branch office and a second appliance 200′ at adata center. In another embodiment, the first appliance 200 and secondappliance 200′ are deployed on the same network 104 or network 104. Forexample, a first appliance 200 may be deployed for a first server farm38, and a second appliance 200 may be deployed for a second server farm38′. In another example, a first appliance 200 may be deployed at afirst branch office while the second appliance 200′ is deployed at asecond branch office'. In some embodiments, the first appliance 200 andsecond appliance 200′ work in cooperation or in conjunction with eachother to accelerate network traffic or the delivery of application anddata between a client and a server

Referring now to FIG. 1C, another embodiment of a network environmentdeploying the appliance 200 with one or more other types of appliances,such as between one or more WAN optimization appliance 205, 205′ isdepicted. For example a first WAN optimization appliance 205 is shownbetween networks 104 and 104′ and a second WAN optimization appliance205′ may be deployed between the appliance 200 and one or more servers106. By way of example, a corporate enterprise may deploy a first WANoptimization appliance 205 at a branch office and a second WANoptimization appliance 205′ at a data center. In some embodiments, theappliance 205 may be located on network 104′. In other embodiments, theappliance 205′ may be located on network 104. In some embodiments, theappliance 205′ may be located on network 104′ or network 104″. In oneembodiment, the appliance 205 and 205′ are on the same network. Inanother embodiment, the appliance 205 and 205′ are on differentnetworks. In another example, a first WAN optimization appliance 205 maybe deployed for a first server farm 38 and a second WAN optimizationappliance 205′ for a second server farm 38′.

In one embodiment, the appliance 205 is a device for accelerating,optimizing or otherwise improving the performance, operation, or qualityof service of any type and form of network traffic, such as traffic toand/or from a WAN connection. In some embodiments, the appliance 205 isa performance enhancing proxy. In other embodiments, the appliance 205is any type and form of WAN optimization or acceleration device,sometimes also referred to as a WAN optimization controller. In oneembodiment, the appliance 205 is any of the product embodiments referredto as WANScaler manufactured by Citrix Systems, Inc. of Ft. Lauderdale,Fla. In other embodiments, the appliance 205 includes any of the productembodiments referred to as BIG-IP link controller and WANjetmanufactured by F5 Networks, Inc. of Seattle, Wash. In anotherembodiment, the appliance 205 includes any of the WX and WXC WANacceleration device platforms manufactured by Juniper Networks, Inc. ofSunnyvale, Calif. In some embodiments, the appliance 205 includes any ofthe steelhead line of WAN optimization appliances manufactured byRiverbed Technology of San Francisco, Calif. In other embodiments, theappliance 205 includes any of the WAN related devices manufactured byExpand Networks Inc. of Roseland, N.J. In one embodiment, the appliance205 includes any of the WAN related appliances manufactured by PacketeerInc. of Cupertino, Calif., such as the PacketShaper, iShared, and SkyXproduct embodiments provided by Packeteer. In yet another embodiment,the appliance 205 includes any WAN related appliances and/or softwaremanufactured by Cisco Systems, Inc. of San Jose, Calif., such as theCisco Wide Area Network Application Services software and networkmodules, and Wide Area Network engine appliances.

In one embodiment, the appliance 205 provides application and dataacceleration services for branch-office or remote offices. In oneembodiment, the appliance 205 includes optimization of Wide Area FileServices (WAFS). In another embodiment, the appliance 205 acceleratesthe delivery of files, such as via the Common Internet File System(CIFS) protocol. In other embodiments, the appliance 205 providescaching in memory and/or storage to accelerate delivery of applicationsand data. In one embodiment, the appliance 205 provides compression ofnetwork traffic at any level of the network stack or at any protocol ornetwork layer. In another embodiment, the appliance 205 providestransport layer protocol optimizations, flow control, performanceenhancements or modifications and/or management to accelerate deliveryof applications and data over a WAN connection. For example, in oneembodiment, the appliance 205 provides Transport Control Protocol (TCP)optimizations. In other embodiments, the appliance 205 providesoptimizations, flow control, performance enhancements or modificationsand/or management for any session or application layer protocol.

In another embodiment, the appliance 205 encoded any type and form ofdata or information into custom or standard TCP and/or IP header fieldsor option fields of network packet to announce presence, functionalityor capability to another appliance 205′. In another embodiment, anappliance 205′ may communicate with another appliance 205′ using dataencoded in both TCP and/or IP header fields or options. For example, theappliance may use TCP option(s) or IP header fields or options tocommunicate one or more parameters to be used by the appliances 205,205′ in performing functionality, such as WAN acceleration, or forworking in conjunction with each other.

In some embodiments, the appliance 200 preserves any of the informationencoded in TCP and/or IP header and/or option fields communicatedbetween appliances 205 and 205′. For example, the appliance 200 mayterminate a transport layer connection traversing the appliance 200,such as a transport layer connection from between a client and a servertraversing appliances 205 and 205′. In one embodiment, the appliance 200identifies and preserves any encoded information in a transport layerpacket transmitted by a first appliance 205 via a first transport layerconnection and communicates a transport layer packet with the encodedinformation to a second appliance 205′ via a second transport layerconnection.

Referring now to FIG. 1D, a network environment for delivering and/oroperating a computing environment on a client 102 is depicted. In someembodiments, a server 106 includes an application delivery system 190for delivering a computing environment or an application and/or datafile to one or more clients 102. In brief overview, a client 10 is incommunication with a server 106 via network 104, 104′ and appliance 200.For example, the client 102 may reside in a remote office of a company,e.g., a branch office, and the server 106 may reside at a corporate datacenter. The client 102 comprises a client agent 120, and a computingenvironment 15. The computing environment 15 may execute or operate anapplication that accesses, processes or uses a data file. The computingenvironment 15, application and/or data file may be delivered via theappliance 200 and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 15, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 15 by the application delivery system 190. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file processable by theapplication from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. The appliance 200 may provide accelerationtechniques for accelerating any transport layer payload from a server106 to a client 102, such as: 1) transport layer connection pooling, 2)transport layer connection multiplexing, 3) transport control protocolbuffering, 4) compression and 5) caching. In some embodiments, theappliance 200 provides load balancing of servers 106 in responding torequests from clients 102. In other embodiments, the appliance 200 actsas a proxy or access server to provide access to the one or more servers106. In another embodiment, the appliance 200 provides a secure virtualprivate network connection from a first network 104 of the client 102 tothe second network 104′ of the server 106, such as an SSL VPNconnection. It yet other embodiments, the appliance 200 providesapplication firewall security, control and management of the connectionand communications between a client 102 and a server 106.

In some embodiments, the application delivery management system 190provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 195. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 190 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 190 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 190 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 190 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 190, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 190, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 190 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 15 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 190 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 15 on client 102.

In some embodiments, the application delivery system 190 comprises anyportion of the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™ and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application delivery system 190 may deliver one ormore applications to clients 102 or users via a remote-display protocolor otherwise via remote-based or server-based computing. In anotherembodiment, the application delivery system 190 may deliver one or moreapplications to clients or users via steaming of the application.

In one embodiment, the application delivery system 190 includes a policyengine 195 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 195 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 195 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 190 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 190 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 190 enumerates a plurality of application programsavailable to the client 102. The application delivery system 190receives a request to execute an enumerated application. The applicationdelivery system 190 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 190 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 190may select a method of execution of the application enabling the localmachine 10 to execute the application program locally after retrieving aplurality of application files comprising the application. In yetanother embodiment, the application delivery system 190 may select amethod of execution of the application to stream the application via thenetwork 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiments the server 106 may display output to the client 102 usingany thin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™, and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application is an ICA client, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla. In other embodiments, theapplication includes a Remote Desktop (RDP) client, developed byMicrosoft Corporation of Redmond, Wash. Also, the server 106 may run anapplication, which for example, may be an application server providingemail services such as Microsoft Exchange manufactured by the MicrosoftCorporation of Redmond, Wash., a web or Internet server, or a desktopsharing server, or a collaboration server. In some embodiments, any ofthe applications may comprise any type of hosted service or products,such as GoToMeeting™ provided by Citrix Online Division, Inc. of SantaBarbara, Calif., WebEx™ provided by WebEx, Inc. of Santa Clara, Calif.,or Microsoft Office Live Meeting provided by Microsoft Corporation ofRedmond, Wash.

Still referring to FIG. 1D, an embodiment of the network environment mayinclude a monitoring server 106A. The monitoring server 106A may includeany type and form performance monitoring service 198. The performancemonitoring service 198 may include monitoring, measurement and/ormanagement software and/or hardware, including data collection,aggregation, analysis, management and reporting. In one embodiment, theperformance monitoring service 198 includes one or more monitoringagents 197. The monitoring agent 197 includes any software, hardware orcombination thereof for performing monitoring, measurement and datacollection activities on a device, such as a client 102, server 106 oran appliance 200, 205. In some embodiments, the monitoring agent 197includes any type and form of script, such as Visual Basic script, orJavascript. In one embodiment, the monitoring agent 197 executestransparently to any application and/or user of the device. In someembodiments, the monitoring agent 197 is installed and operatedunobtrusively to the application or client. In yet another embodiment,the monitoring agent 197 is installed and operated without anyinstrumentation for the application or device.

In some embodiments, the monitoring agent 197 monitors, measures andcollects data on a predetermined frequency. In other embodiments, themonitoring agent 197 monitors, measures and collects data based upondetection of any type and form of event. For example, the monitoringagent 197 may collect data upon detection of a request for a web page orreceipt of an HTTP response. In another example, the monitoring agent197 may collect data upon detection of any user input events, such as amouse click. The monitoring agent 197 may report or provide anymonitored, measured or collected data to the monitoring service 198. Inone embodiment, the monitoring agent 197 transmits information to themonitoring service 198 according to a schedule or a predeterminedfrequency. In another embodiment, the monitoring agent 197 transmitsinformation to the monitoring service 198 upon detection of an event.

In some embodiments, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of any networkresource or network infrastructure element, such as a client, server,server farm, appliance 200, appliance 205, or network connection. In oneembodiment, the monitoring service 198 and/or monitoring agent 197performs monitoring and performance measurement of any transport layerconnection, such as a TCP or UDP connection. In another embodiment, themonitoring service 198 and/or monitoring agent 197 monitors and measuresnetwork latency. In yet one embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures bandwidth utilization.

In other embodiments, the monitoring service 198 and/or monitoring agent197 monitors and measures end-user response times. In some embodiments,the monitoring service 198 performs monitoring and performancemeasurement of an application. In another embodiment, the monitoringservice 198 and/or monitoring agent 197 performs monitoring andperformance measurement of any session or connection to the application.In one embodiment, the monitoring service 198 and/or monitoring agent197 monitors and measures performance of a browser. In anotherembodiment, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of HTTP based transactions. In someembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of a Voice over IP (VoIP) applicationor session. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors and measures performance of a remotedisplay protocol application, such as an ICA client or RDP client. Inyet another embodiment, the monitoring service 198 and/or monitoringagent 197 monitors and measures performance of any type and form ofstreaming media. In still a further embodiment, the monitoring service198 and/or monitoring agent 197 monitors and measures performance of ahosted application or a Software-As-A-Service (SaaS) delivery model.

In some embodiments, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of one or moretransactions, requests or responses related to application. In otherembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures any portion of an application layer stack, such asany .NET or J2EE calls. In one embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures database or SQLtransactions. In yet another embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures any method, functionor application programming interface (API) call.

In one embodiment, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of a delivery ofapplication and/or data from a server to a client via one or moreappliances, such as appliance 200 and/or appliance 205. In someembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of delivery of a virtualizedapplication. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors and measures performance of delivery of astreaming application. In another embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures performance ofdelivery of a desktop application to a client and/or the execution ofthe desktop application on the client. In another embodiment, themonitoring service 198 and/or monitoring agent 197 monitors and measuresperformance of a client/server application.

In one embodiment, the monitoring service 198 and/or monitoring agent197 is designed and constructed to provide application performancemanagement for the application delivery system 190. For example, themonitoring service 198 and/or monitoring agent 197 may monitor, measureand manage the performance of the delivery of applications via theCitrix Presentation Server. In this example, the monitoring service 198and/or monitoring agent 197 monitors individual ICA sessions. Themonitoring service 198 and/or monitoring agent 197 may measure the totaland per session system resource usage, as well as application andnetworking performance. The monitoring service 198 and/or monitoringagent 197 may identify the active servers for a given user and/or usersession. In some embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors back-end connections between theapplication delivery system 190 and an application and/or databaseserver. The monitoring service 198 and/or monitoring agent 197 maymeasure network latency, delay and volume per user-session or ICAsession.

In some embodiments, the monitoring service 198 and/or monitoring agent197 measures and monitors memory usage for the application deliverysystem 190, such as total memory usage, per user session and/or perprocess. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 measures and monitors CPU usage the applicationdelivery system 190, such as total CPU usage, per user session and/orper process. In another embodiments, the monitoring service 198 and/ormonitoring agent 197 measures and monitors the time to log-in to anapplication, a server, or the application delivery system, such asCitrix Presentation Server. In one embodiment, the monitoring service198 and/or monitoring agent 197 measures and monitors the duration auser is logged into an application, a server, or the applicationdelivery system 190. In some embodiments, the monitoring service 198and/or monitoring agent 197 measures and monitors active and inactivesession counts for an application, server or application delivery systemsession. In yet another embodiment, the monitoring service 198 and/ormonitoring agent 197 measures and monitors user session latency.

In yet further embodiments, the monitoring service 198 and/or monitoringagent 197 measures and monitors measures and monitors any type and formof server metrics. In one embodiment, the monitoring service 198 and/ormonitoring agent 197 measures and monitors metrics related to systemmemory, CPU usage, and disk storage. In another embodiment, themonitoring service 198 and/or monitoring agent 197 measures and monitorsmetrics related to page faults, such as page faults per second. In otherembodiments, the monitoring service 198 and/or monitoring agent 197measures and monitors round-trip time metrics. In yet anotherembodiment, the monitoring service 198 and/or monitoring agent 197measures and monitors metrics related to application crashes, errorsand/or hangs.

In some embodiments, the monitoring service 198 and monitoring agent 198includes any of the product embodiments referred to as EdgeSightmanufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla. In anotherembodiment, the performance monitoring service 198 and/or monitoringagent 198 includes any portion of the product embodiments referred to asthe TrueView product suite manufactured by the Symphoniq Corporation ofPalo Alto, Calif. In one embodiment, the performance monitoring service198 and/or monitoring agent 198 includes any portion of the productembodiments referred to as the TeaLeaf CX product suite manufactured bythe TeaLeaf Technology Inc. of San Francisco, Calif. In otherembodiments, the performance monitoring service 198 and/or monitoringagent 198 includes any portion of the business service managementproducts, such as the BMC Performance Manager and Patrol products,manufactured by BMC Software, Inc. of Houston, Tex.

The client 102, server 106, and appliance 200 may be deployed as and/orexecuted on any type and form of computing device, such as a computer,network device or appliance capable of communicating on any type andform of network and performing the operations described herein. FIGS. 1Eand 1F depict block diagrams of a computing device 100 useful forpracticing an embodiment of the client 102, server 106 or appliance 200.As shown in FIGS. 1E and 1F, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1E, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1E, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1F depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1F the main memory 122 maybe DRDRAM.

FIG. 1F depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1F, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1F depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130 bvia HyperTransport, Rapid I/O, or InfiniBand. FIG. 1F also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 b using a localinterconnect bus while communicating with I/O device 130 a directly. Thecomputing device 100 may support any suitable installation device 116,such as a floppy disk drive for receiving floppy disks such as 3.5-inch,5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive, a DVD-ROMdrive, tape drives of various formats, USB device, hard-drive or anyother device suitable for installing software and programs such as anyclient agent 120, or portion thereof. The computing device 100 mayfurther include a storage device, such as one or more hard disk drivesor redundant arrays of independent disks, for storing an operatingsystem and other related software, and for storing application softwareprograms such as any program or software 120 for implementing (e.g.,software 120 configured, designed and/or customized for) the systems andmethods described herein. Optionally, any of the installation devices116 could also be used as the storage device 128. Additionally, theoperating system and the software can be run from a bootable medium, forexample, a bootable CD, such as KNOPPIX®, a bootable CD for GNU/Linuxthat is available as a GNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein.

A wide variety of I/O devices 130 a-130 n may be present in thecomputing device 100. Input devices include keyboards, mice, trackpads,trackballs, microphones, and drawing tablets. Output devices includevideo displays, speakers, inkjet printers, laser printers, anddye-sublimation printers. The I/O devices 130 may be controlled by anI/O controller 123 as shown in FIG. 1E. The I/O controller may controlone or more I/O devices such as a keyboard 126 and a pointing device127, e.g., a mouse or optical pen. Furthermore, an I/O device may alsoprovide storage 128 and/or an installation medium 116 for the computingdevice 100. In still other embodiments, the computing device 100 mayprovide USB connections to receive handheld USB storage devices such asthe USB Flash Drive line of devices manufactured by Twintech Industry,Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, an I/O device 130 may be a bridge 170 betweenthe system bus 150 and an external communication bus, such as a USB bus,an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, aFireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, aGigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, aSuper HIPPI bus, a SerialPlus bus, a SCl/LAMP bus, a FibreChannel bus,or a Serial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1E and 1F typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, Calif.; OS/2, manufacturedby International Business Machines of Armonk, N.Y.; and Linux, afreely-available operating system distributed by Caldera Corp. of SaltLake City, Utah, or any type and/or form of a Unix operating system,among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

As shown in FIG. 1G, the computing device 100 may comprise multipleprocessors and may provide functionality for simultaneous execution ofinstructions or for simultaneous execution of one instruction on morethan one piece of data. In some embodiments, the computing device 100may comprise a parallel processor with one or more cores. In one ofthese embodiments, the computing device 100 is a shared memory paralleldevice, with multiple processors and/or multiple processor cores,accessing all available memory as a single global address space. Inanother of these embodiments, the computing device 100 is a distributedmemory parallel device with multiple processors each accessing localmemory only. In still another of these embodiments, the computing device100 has both some memory which is shared and some memory which can onlybe accessed by particular processors or subsets of processors. In stilleven another of these embodiments, the computing device 100, such as amulti-core microprocessor, combines two or more independent processorsinto a single package, often a single integrated circuit (IC). In yetanother of these embodiments, the computing device 100 includes a chiphaving a CELL BROADBAND ENGINE architecture and including a Powerprocessor element and a plurality of synergistic processing elements,the Power processor element and the plurality of synergistic processingelements linked together by an internal high speed bus, which may bereferred to as an element interconnect bus.

In some embodiments, the processors provide functionality for executionof a single instruction simultaneously on multiple pieces of data(SIMD). In other embodiments, the processors provide functionality forexecution of multiple instructions simultaneously on multiple pieces ofdata (MIMD). In still other embodiments, the processor may use anycombination of SIMD and MIMD cores in a single device.

In some embodiments, the computing device 100 may comprise a graphicsprocessing unit. In one of these embodiments, depicted in FIG. 1H, thecomputing device 100 includes at least one central processing unit 101and at least one graphics processing unit. In another of theseembodiments, the computing device 100 includes at least one parallelprocessing unit and at least one graphics processing unit. In stillanother of these embodiments, the computing device 100 includes aplurality of processing units of any type, one of the plurality ofprocessing units comprising a graphics processing unit.

In some embodiments, a first computing device 100 a executes anapplication on behalf of a user of a client computing device 100 b. Inother embodiments, a computing device 100 a executes a virtual machine,which provides an execution session within which applications execute onbehalf of a user or a client computing devices 100 b. In one of theseembodiments, the execution session is a hosted desktop session. Inanother of these embodiments, the computing device 100 executes aterminal services session. The terminal services session may provide ahosted desktop environment. In still another of these embodiments, theexecution session provides access to a computing environment, which maycomprise one or more of: an application, a plurality of applications, adesktop application, and a desktop session in which one or moreapplications may execute.

B. Appliance Architecture

FIG. 2A illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting. As shown in FIG.2, appliance 200 comprises a hardware layer 206 and a software layerdivided into a user space 202 and a kernel space 204.

Hardware layer 206 provides the hardware elements upon which programsand services within kernel space 204 and user space 202 are executed.Hardware layer 206 also provides the structures and elements which allowprograms and services within kernel space 204 and user space 202 tocommunicate data both internally and externally with respect toappliance 200. As shown in FIG. 2, the hardware layer 206 includes aprocessing unit 262 for executing software programs and services, amemory 264 for storing software and data, network ports 266 fortransmitting and receiving data over a network, and an encryptionprocessor 260 for performing functions related to Secure Sockets Layerprocessing of data transmitted and received over the network. In someembodiments, the central processing unit 262 may perform the functionsof the encryption processor 260 in a single processor. Additionally, thehardware layer 206 may comprise multiple processors for each of theprocessing unit 262 and the encryption processor 260. The processor 262may include any of the processors 101 described above in connection withFIGS. 1E and 1F. For example, in one embodiment, the appliance 200comprises a first processor 262 and a second processor 262′. In otherembodiments, the processor 262 or 262′ comprises a multi-core processor.

Although the hardware layer 206 of appliance 200 is generallyillustrated with an encryption processor 260, processor 260 may be aprocessor for performing functions related to any encryption protocol,such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)protocol. In some embodiments, the processor 260 may be a generalpurpose processor (GPP), and in further embodiments, may have executableinstructions for performing processing of any security related protocol.

Although the hardware layer 206 of appliance 200 is illustrated withcertain elements in FIG. 2, the hardware portions or components ofappliance 200 may comprise any type and form of elements, hardware orsoftware, of a computing device, such as the computing device 100illustrated and discussed herein in conjunction with FIGS. 1E and 1F. Insome embodiments, the appliance 200 may comprise a server, gateway,router, switch, bridge or other type of computing or network device, andhave any hardware and/or software elements associated therewith.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into kernel space 204 and userspace 204. In example software architecture 200, the operating systemmay be any type and/or form of Unix operating system although theinvention is not so limited. As such, the appliance 200 can be runningany operating system such as any of the versions of the Microsoft®Windows operating systems, the different releases of the Unix and Linuxoperating systems, any version of the Mac OS® for Macintosh computers,any embedded operating system, any network operating system, anyreal-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices or network devices, or any other operating system capable ofrunning on the appliance 200 and performing the operations describedherein.

The kernel space 204 is reserved for running the kernel 230, includingany device drivers, kernel extensions or other kernel related software.As known to those skilled in the art, the kernel 230 is the core of theoperating system, and provides access, control, and management ofresources and hardware-related elements of the application 104. Inaccordance with an embodiment of the appliance 200, the kernel space 204also includes a number of network services or processes working inconjunction with a cache manager 232, sometimes also referred to as theintegrated cache, the benefits of which are described in detail furtherherein. Additionally, the embodiment of the kernel 230 will depend onthe embodiment of the operating system installed, configured, orotherwise used by the device 200.

In one embodiment, the device 200 comprises one network stack 267, suchas a TCP/IP based stack, for communicating with the client 102 and/orthe server 106. In one embodiment, the network stack 267 is used tocommunicate with a first network, such as network 108, and a secondnetwork 110. In some embodiments, the device 200 terminates a firsttransport layer connection, such as a TCP connection of a client 102,and establishes a second transport layer connection to a server 106 foruse by the client 102, e.g., the second transport layer connection isterminated at the appliance 200 and the server 106. The first and secondtransport layer connections may be established via a single networkstack 267. In other embodiments, the device 200 may comprise multiplenetwork stacks, for example 267 and 267′, and the first transport layerconnection may be established or terminated at one network stack 267,and the second transport layer connection on the second network stack267′. For example, one network stack may be for receiving andtransmitting network packet on a first network, and another networkstack for receiving and transmitting network packets on a secondnetwork. In one embodiment, the network stack 267 comprises a buffer 243for queuing one or more network packets for transmission by theappliance 200.

As shown in FIG. 2, the kernel space 204 includes the cache manager 232,a high-speed layer 2-7 integrated packet engine 240, an encryptionengine 234, a policy engine 236 and multi-protocol compression logic238. Running these components or processes 232, 240, 234, 236 and 238 inkernel space 204 or kernel mode instead of the user space 202 improvesthe performance of each of these components, alone and in combination.Kernel operation means that these components or processes 232, 240, 234,236 and 238 run in the core address space of the operating system of thedevice 200. For example, running the encryption engine 234 in kernelmode improves encryption performance by moving encryption and decryptionoperations to the kernel, thereby reducing the number of transitionsbetween the memory space or a kernel thread in kernel mode and thememory space or a thread in user mode. For example, data obtained inkernel mode may not need to be passed or copied to a process or threadrunning in user mode, such as from a kernel level data structure to auser level data structure. In another aspect, the number of contextswitches between kernel mode and user mode are also reduced.Additionally, synchronization of and communications between any of thecomponents or processes 232, 240, 235, 236 and 238 can be performed moreefficiently in the kernel space 204.

In some embodiments, any portion of the components 232, 240, 234, 236and 238 may run or operate in the kernel space 204, while other portionsof these components 232, 240, 234, 236 and 238 may run or operate inuser space 202. In one embodiment, the appliance 200 uses a kernel-leveldata structure providing access to any portion of one or more networkpackets, for example, a network packet comprising a request from aclient 102 or a response from a server 106. In some embodiments, thekernel-level data structure may be obtained by the packet engine 240 viaa transport layer driver interface or filter to the network stack 267.The kernel-level data structure may comprise any interface and/or dataaccessible via the kernel space 204 related to the network stack 267,network traffic or packets received or transmitted by the network stack267. In other embodiments, the kernel-level data structure may be usedby any of the components or processes 232, 240, 234, 236 and 238 toperform the desired operation of the component or process. In oneembodiment, a component 232, 240, 234, 236 and 238 is running in kernelmode 204 when using the kernel-level data structure, while in anotherembodiment, the component 232, 240, 234, 236 and 238 is running in usermode when using the kernel-level data structure. In some embodiments,the kernel-level data structure may be copied or passed to a secondkernel-level data structure, or any desired user-level data structure.

The cache manager 232 may comprise software, hardware or any combinationof software and hardware to provide cache access, control and managementof any type and form of content, such as objects or dynamicallygenerated objects served by the originating servers 106. The data,objects or content processed and stored by the cache manager 232 maycomprise data in any format, such as a markup language, or communicatedvia any protocol. In some embodiments, the cache manager 232 duplicatesoriginal data stored elsewhere or data previously computed, generated ortransmitted, in which the original data may need longer access time tofetch, compute or otherwise obtain relative to reading a cache memoryelement. Once the data is stored in the cache memory element, future usecan be made by accessing the cached copy rather than refetching orrecomputing the original data, thereby reducing the access time. In someembodiments, the cache memory element may comprise a data object inmemory 264 of device 200. In other embodiments, the cache memory elementmay comprise memory having a faster access time than memory 264. Inanother embodiment, the cache memory element may comprise any type andform of storage element of the device 200, such as a portion of a harddisk. In some embodiments, the processing unit 262 may provide cachememory for use by the cache manager 232. In yet further embodiments, thecache manager 232 may use any portion and combination of memory,storage, or the processing unit for caching data, objects, and othercontent.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any embodiments of the techniques of theappliance 200 described herein. For example, the cache manager 232includes logic or functionality to invalidate objects based on theexpiration of an invalidation time period or upon receipt of aninvalidation command from a client 102 or server 106. In someembodiments, the cache manager 232 may operate as a program, service,process or task executing in the kernel space 204, and in otherembodiments, in the user space 202. In one embodiment, a first portionof the cache manager 232 executes in the user space 202 while a secondportion executes in the kernel space 204. In some embodiments, the cachemanager 232 can comprise any type of general purpose processor (GPP), orany other type of integrated circuit, such as a Field Programmable GateArray (FPGA), Programmable Logic Device (PLD), or Application SpecificIntegrated Circuit (ASIC).

The policy engine 236 may include, for example, an intelligentstatistical engine or other programmable application(s). In oneembodiment, the policy engine 236 provides a configuration mechanism toallow a user to identify, specify, define or configure a caching policy.Policy engine 236, in some embodiments, also has access to memory tosupport data structures such as lookup tables or hash tables to enableuser-selected caching policy decisions. In other embodiments, the policyengine 236 may comprise any logic, rules, functions or operations todetermine and provide access, control and management of objects, data orcontent being cached by the appliance 200 in addition to access, controland management of security, network traffic, network access, compressionor any other function or operation performed by the appliance 200.Further examples of specific caching policies are further describedherein.

The encryption engine 234 comprises any logic, business rules, functionsor operations for handling the processing of any security relatedprotocol, such as SSL or TLS, or any function related thereto. Forexample, the encryption engine 234 encrypts and decrypts networkpackets, or any portion thereof, communicated via the appliance 200. Theencryption engine 234 may also setup or establish SSL or TLS connectionson behalf of the client 102 a-102 n, server 106 a-106 n, or appliance200. As such, the encryption engine 234 provides offloading andacceleration of SSL processing. In one embodiment, the encryption engine234 uses a tunneling protocol to provide a virtual private networkbetween a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine 234 is in communication with theEncryption processor 260. In other embodiments, the encryption engine234 comprises executable instructions running on the Encryptionprocessor 260.

The multi-protocol compression engine 238 comprises any logic, businessrules, function or operations for compressing one or more protocols of anetwork packet, such as any of the protocols used by the network stack267 of the device 200. In one embodiment, multi-protocol compressionengine 238 compresses bi-directionally between clients 102 a-102 n andservers 106 a-106 n any TCP/IP based protocol, including MessagingApplication Programming Interface (MAPI) (email), File Transfer Protocol(FTP), HyperText Transfer Protocol (HTTP), Common Internet File System(CIFS) protocol (file transfer), Independent Computing Architecture(ICA) protocol, Remote Desktop Protocol (RDP), Wireless ApplicationProtocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP) protocol.In other embodiments, multi-protocol compression engine 238 providescompression of Hypertext Markup Language (HTML) based protocols and insome embodiments, provides compression of any markup languages, such asthe Extensible Markup Language (XML). In one embodiment, themulti-protocol compression engine 238 provides compression of anyhigh-performance protocol, such as any protocol designed for appliance200 to appliance 200 communications. In another embodiment, themulti-protocol compression engine 238 compresses any payload of or anycommunication using a modified transport control protocol, such asTransaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),TCP with large windows (TCP-LW), a congestion prediction protocol suchas the TCP-Vegas protocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine 238 by executing in the kernel mode204 and integrating with packet processing engine 240 accessing thenetwork stack 267 is able to compress any of the protocols carried bythe TCP/IP protocol, such as any application layer protocol.

High speed layer 2-7 integrated packet engine 240, also generallyreferred to as a packet processing engine or packet engine, isresponsible for managing the kernel-level processing of packets receivedand transmitted by appliance 200 via network ports 266. The high speedlayer 2-7 integrated packet engine 240 may comprise a buffer for queuingone or more network packets during processing, such as for receipt of anetwork packet or transmission of a network packet. Additionally, thehigh speed layer 2-7 integrated packet engine 240 is in communicationwith one or more network stacks 267 to send and receive network packetsvia network ports 266. The high speed layer 2-7 integrated packet engine240 works in conjunction with encryption engine 234, cache manager 232,policy engine 236 and multi-protocol compression logic 238. Inparticular, encryption engine 234 is configured to perform SSLprocessing of packets, policy engine 236 is configured to performfunctions related to traffic management such as request-level contentswitching and request-level cache redirection, and multi-protocolcompression logic 238 is configured to perform functions related tocompression and decompression of data.

The high speed layer 2-7 integrated packet engine 240 includes a packetprocessing timer 242. In one embodiment, the packet processing timer 242provides one or more time intervals to trigger the processing ofincoming, i.e., received, or outgoing, i.e., transmitted, networkpackets. In some embodiments, the high speed layer 2-7 integrated packetengine 240 processes network packets responsive to the timer 242. Thepacket processing timer 242 provides any type and form of signal to thepacket engine 240 to notify, trigger, or communicate a time relatedevent, interval or occurrence. In many embodiments, the packetprocessing timer 242 operates in the order of milliseconds, such as forexample 100 ms, 50 ms or 25 ms. For example, in some embodiments, thepacket processing timer 242 provides time intervals or otherwise causesa network packet to be processed by the high speed layer 2-7 integratedpacket engine 240 at a 10 ms time interval, while in other embodiments,at a 5 ms time interval, and still yet in further embodiments, as shortas a 3, 2, or 1 ms time interval. The high speed layer 2-7 integratedpacket engine 240 may be interfaced, integrated or in communication withthe encryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression engine 238 during operation. As such, any ofthe logic, functions, or operations of the encryption engine 234, cachemanager 232, policy engine 236 and multi-protocol compression logic 238may be performed responsive to the packet processing timer 242 and/orthe packet engine 240. Therefore, any of the logic, functions, oroperations of the encryption engine 234, cache manager 232, policyengine 236 and multi-protocol compression logic 238 may be performed atthe granularity of time intervals provided via the packet processingtimer 242, for example, at a time interval of less than or equal to 10ms. For example, in one embodiment, the cache manager 232 may performinvalidation of any cached objects responsive to the high speed layer2-7 integrated packet engine 240 and/or the packet processing timer 242.In another embodiment, the expiry or invalidation time of a cachedobject can be set to the same order of granularity as the time intervalof the packet processing timer 242, such as at every 10 ms.

In contrast to kernel space 204, user space 202 is the memory area orportion of the operating system used by user mode applications orprograms otherwise running in user mode. A user mode application may notaccess kernel space 204 directly and uses service calls in order toaccess kernel services. As shown in FIG. 2, user space 202 of appliance200 includes a graphical user interface (GUI) 210, a command lineinterface (CLI) 212, shell services 214, health monitoring program 216,and daemon services 218. GUI 210 and CLI 212 provide a means by which asystem administrator or other user can interact with and control theoperation of appliance 200, such as via the operating system of theappliance 200. The GUI 210 or CLI 212 can comprise code running in userspace 202 or kernel space 204. The GUI 210 may be any type and form ofgraphical user interface and may be presented via text, graphical orotherwise, by any type of program or application, such as a browser. TheCLI 212 may be any type and form of command line or text-basedinterface, such as a command line provided by the operating system. Forexample, the CLI 212 may comprise a shell, which is a tool to enableusers to interact with the operating system. In some embodiments, theCLI 212 may be provided via a bash, csh, tcsh, or ksh type shell. Theshell services 214 comprises the programs, services, tasks, processes orexecutable instructions to support interaction with the appliance 200 oroperating system by a user via the GUI 210 and/or CLI 212.

Health monitoring program 216 is used to monitor, check, report andensure that network systems are functioning properly and that users arereceiving requested content over a network. Health monitoring program216 comprises one or more programs, services, tasks, processes orexecutable instructions to provide logic, rules, functions or operationsfor monitoring any activity of the appliance 200. In some embodiments,the health monitoring program 216 intercepts and inspects any networktraffic passed via the appliance 200. In other embodiments, the healthmonitoring program 216 interfaces by any suitable means and/ormechanisms with one or more of the following: the encryption engine 234,cache manager 232, policy engine 236, multi-protocol compression logic238, packet engine 240, daemon services 218, and shell services 214. Assuch, the health monitoring program 216 may call any applicationprogramming interface (API) to determine a state, status, or health ofany portion of the appliance 200. For example, the health monitoringprogram 216 may ping or send a status inquiry on a periodic basis tocheck if a program, process, service or task is active and currentlyrunning. In another example, the health monitoring program 216 may checkany status, error or history logs provided by any program, process,service or task to determine any condition, status or error with anyportion of the appliance 200.

Daemon services 218 are programs that run continuously or in thebackground and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests toother programs or processes, such as another daemon service 218 asappropriate. As known to those skilled in the art, a daemon service 218may run unattended to perform continuous or periodic system widefunctions, such as network control, or to perform any desired task. Insome embodiments, one or more daemon services 218 run in the user space202, while in other embodiments, one or more daemon services 218 run inthe kernel space.

Referring now to FIG. 2B, another embodiment of the appliance 200 isdepicted. In brief overview, the appliance 200 provides one or more ofthe following services, functionality or operations: SSL VPNconnectivity 280, switching/load balancing 284, Domain Name Serviceresolution 286, acceleration 288 and an application firewall 290 forcommunications between one or more clients 102 and one or more servers106. Each of the servers 106 may provide one or more network relatedservices 270 a-270 n (referred to as services 270). For example, aserver 106 may provide an http service 270. The appliance 200 comprisesone or more virtual servers or virtual internet protocol servers,referred to as a vServer, VIP server, or just VIP 275 a-275 n (alsoreferred herein as vServer 275). The vServer 275 receives, intercepts orotherwise processes communications between a client 102 and a server 106in accordance with the configuration and operations of the appliance200.

The vServer 275 may comprise software, hardware or any combination ofsoftware and hardware. The vServer 275 may comprise any type and form ofprogram, service, task, process or executable instructions operating inuser mode 202, kernel mode 204 or any combination thereof in theappliance 200. The vServer 275 includes any logic, functions, rules, oroperations to perform any embodiments of the techniques describedherein, such as SSL VPN 280, switching/load balancing 284, Domain NameService resolution 286, acceleration 288 and an application firewall290. In some embodiments, the vServer 275 establishes a connection to aservice 270 of a server 106. The service 275 may comprise any program,application, process, task or set of executable instructions capable ofconnecting to and communicating to the appliance 200, client 102 orvServer 275. For example, the service 275 may comprise a web server,http server, ftp, email or database server. In some embodiments, theservice 270 is a daemon process or network driver for listening,receiving and/or sending communications for an application, such asemail, database or an enterprise application. In some embodiments, theservice 270 may communicate on a specific IP address, or IP address andport.

In some embodiments, the vServer 275 applies one or more policies of thepolicy engine 236 to network communications between the client 102 andserver 106. In one embodiment, the policies are associated with avServer 275. In another embodiment, the policies are based on a user, ora group of users. In yet another embodiment, a policy is global andapplies to one or more vServers 275 a-275 n, and any user or group ofusers communicating via the appliance 200. In some embodiments, thepolicies of the policy engine have conditions upon which the policy isapplied based on any content of the communication, such as internetprotocol address, port, protocol type, header or fields in a packet, orthe context of the communication, such as user, group of the user,vServer 275, transport layer connection, and/or identification orattributes of the client 102 or server 106.

In other embodiments, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to access the computingenvironment 15, application, and/or data file from a server 106. Inanother embodiment, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to have the application deliverysystem 190 deliver one or more of the computing environment 15,application, and/or data file. In yet another embodiment, the appliance200 establishes a VPN or SSL VPN connection based on the policy engine's236 authentication and/or authorization of a remote user or a remoteclient 102 In one embodiment, the appliance 200 controls the flow ofnetwork traffic and communication sessions based on policies of thepolicy engine 236. For example, the appliance 200 may control the accessto a computing environment 15, application or data file based on thepolicy engine 236.

In some embodiments, the vServer 275 establishes a transport layerconnection, such as a TCP or UDP connection with a client 102 via theclient agent 120. In one embodiment, the vServer 275 listens for andreceives communications from the client 102. In other embodiments, thevServer 275 establishes a transport layer connection, such as a TCP orUDP connection with a client server 106. In one embodiment, the vServer275 establishes the transport layer connection to an internet protocoladdress and port of a server 270 running on the server 106. In anotherembodiment, the vServer 275 associates a first transport layerconnection to a client 102 with a second transport layer connection tothe server 106. In some embodiments, a vServer 275 establishes a pool oftransport layer connections to a server 106 and multiplexes clientrequests via the pooled transport layer connections.

In some embodiments, the appliance 200 provides a SSL VPN connection 280between a client 102 and a server 106. For example, a client 102 on afirst network 102 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104′ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, the clientagent 120 intercepts communications of the client 102 on the firstnetwork 104, encrypts the communications, and transmits thecommunications via a first transport layer connection to the appliance200. The appliance 200 associates the first transport layer connectionon the first network 104 to a second transport layer connection to theserver 106 on the second network 104. The appliance 200 receives theintercepted communication from the client agent 102, decrypts thecommunications, and transmits the communication to the server 106 on thesecond network 104 via the second transport layer connection. The secondtransport layer connection may be a pooled transport layer connection.As such, the appliance 200 provides an end-to-end secure transport layerconnection for the client 102 between the two networks 104, 104′.

In one embodiment, the appliance 200 hosts an intranet internet protocolor IntranetIP 282 address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 200,the appliance 200 establishes, assigns or otherwise provides anIntranetIP address 282, which is a network identifier, such as IPaddress and/or host name, for the client 102 on the second network 104′.The appliance 200 listens for and receives on the second or privatenetwork 104′ for any communications directed towards the client 102using the client's established IntranetIP 282. In one embodiment, theappliance 200 acts as or on behalf of the client 102 on the secondprivate network 104. For example, in another embodiment, a vServer 275listens for and responds to communications to the IntranetIP 282 of theclient 102. In some embodiments, if a computing device 100 on the secondnetwork 104′ transmits a request, the appliance 200 processes therequest as if it were the client 102. For example, the appliance 200 mayrespond to a ping to the client's IntranetIP 282. In another example,the appliance may establish a connection, such as a TCP or UDPconnection, with computing device 100 on the second network 104requesting a connection with the client's IntranetIP 282.

In some embodiments, the appliance 200 provides one or more of thefollowing acceleration techniques 288 to communications between theclient 102 and server 106: 1) compression; 2) decompression; 3)Transmission Control Protocol pooling; 4) Transmission Control Protocolmultiplexing; 5) Transmission Control Protocol buffering; and 6)caching. In one embodiment, the appliance 200 relieves servers 106 ofmuch of the processing load caused by repeatedly opening and closingtransport layers connections to clients 102 by opening one or moretransport layer connections with each server 106 and maintaining theseconnections to allow repeated data accesses by clients via the Internet.This technique is referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 200 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction may berequired. For example, in the case of an in-bound packet (that is, apacket received from a client 102), the source network address of thepacket is changed to that of an output port of appliance 200, and thedestination network address is changed to that of the intended server.In the case of an outbound packet (that is, one received from a server106), the source network address is changed from that of the server 106to that of an output port of appliance 200 and the destination addressis changed from that of appliance 200 to that of the requesting client102. The sequence numbers and acknowledgment numbers of the packet arealso translated to sequence numbers and acknowledgement numbers expectedby the client 102 on the appliance's 200 transport layer connection tothe client 102. In some embodiments, the packet checksum of thetransport layer protocol is recalculated to account for thesetranslations.

In another embodiment, the appliance 200 provides switching orload-balancing functionality 284 for communications between the client102 and server 106. In some embodiments, the appliance 200 distributestraffic and directs client requests to a server 106 based on layer 4 orapplication-layer request data. In one embodiment, although the networklayer or layer 2 of the network packet identifies a destination server106, the appliance 200 determines the server 106 to distribute thenetwork packet by application information and data carried as payload ofthe transport layer packet. In one embodiment, the health monitoringprograms 216 of the appliance 200 monitor the health of servers todetermine the server 106 for which to distribute a client's request. Insome embodiments, if the appliance 200 detects a server 106 is notavailable or has a load over a predetermined threshold, the appliance200 can direct or distribute client requests to another server 106.

In some embodiments, the appliance 200 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts a DNS requesttransmitted by the client 102. In one embodiment, the appliance 200responds to a client's DNS request with an IP address of or hosted bythe appliance 200. In this embodiment, the client 102 transmits networkcommunication for the domain name to the appliance 200. In anotherembodiment, the appliance 200 responds to a client's DNS request with anIP address of or hosted by a second appliance 200′. In some embodiments,the appliance 200 responds to a client's DNS request with an IP addressof a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 200 provides applicationfirewall functionality 290 for communications between the client 102 andserver 106. In one embodiment, the policy engine 236 provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall 290 protects against denial of service (DoS)attacks. In other embodiments, the appliance inspects the content ofintercepted requests to identify and block application-based attacks. Insome embodiments, the rules/policy engine 236 comprises one or moreapplication firewall or security control policies for providingprotections against various classes and types of web or Internet basedvulnerabilities, such as one or more of the following: 1) bufferoverflow, 2) CGI-BIN parameter manipulation, 3) form/hidden fieldmanipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)broken access control list (ACLs) or weak passwords, 7) cross-sitescripting (XSS), 8) command injection, 9) SQL injection, 10) errortriggering sensitive information leak, 11) insecure use of cryptography,12) server misconfiguration, 13) back doors and debug options, 14)website defacement, 15) platform or operating systems vulnerabilities,and 16) zero-day exploits. In an embodiment, the application firewall290 provides HTML form field protection in the form of inspecting oranalyzing the network communication for one or more of the following: 1)some required fields are returned, 2) no added field allowed, 3)read-only and hidden field enforcement, 4) drop-down list and radiobutton field conformance, and 5) form-field max-length enforcement. Insome embodiments, the application firewall 290 ensures cookies are notmodified. In other embodiments, the application firewall 290 protectsagainst forceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall 290 protectsany confidential information contained in the network communication. Theapplication firewall 290 may inspect or analyze any networkcommunication in accordance with the rules or polices of the engine 236to identify any confidential information in any field of the networkpacket. In some embodiments, the application firewall 290 identifies inthe network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay comprise these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall 290 maytake a policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall 290 may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

Still referring to FIG. 2B, the appliance 200 may include a performancemonitoring agent 197 as discussed above in conjunction with FIG. 1D. Inone embodiment, the appliance 200 receives the monitoring agent 197 fromthe monitoring service 198 or monitoring server 106 as depicted in FIG.1D. In some embodiments, the appliance 200 stores the monitoring agent197 in storage, such as disk, for delivery to any client or server incommunication with the appliance 200. For example, in one embodiment,the appliance 200 transmits the monitoring agent 197 to a client uponreceiving a request to establish a transport layer connection. In otherembodiments, the appliance 200 transmits the monitoring agent 197 uponestablishing the transport layer connection with the client 102. Inanother embodiment, the appliance 200 transmits the monitoring agent 197to the client upon intercepting or detecting a request for a web page.In yet another embodiment, the appliance 200 transmits the monitoringagent 197 to a client or a server in response to a request from themonitoring server 198. In one embodiment, the appliance 200 transmitsthe monitoring agent 197 to a second appliance 200′ or appliance 205.

In other embodiments, the appliance 200 executes the monitoring agent197. In one embodiment, the monitoring agent 197 measures and monitorsthe performance of any application, program, process, service, task orthread executing on the appliance 200. For example, the monitoring agent197 may monitor and measure performance and operation of vServers275A-275N. In another embodiment, the monitoring agent 197 measures andmonitors the performance of any transport layer connections of theappliance 200. In some embodiments, the monitoring agent 197 measuresand monitors the performance of any user sessions traversing theappliance 200. In one embodiment, the monitoring agent 197 measures andmonitors the performance of any virtual private network connectionsand/or sessions traversing the appliance 200, such as an SSL VPNsession. In still further embodiments, the monitoring agent 197 measuresand monitors the memory, CPU and disk usage and performance of theappliance 200. In yet another embodiment, the monitoring agent 197measures and monitors the performance of any acceleration technique 288performed by the appliance 200, such as SSL offloading, connectionpooling and multiplexing, caching, and compression. In some embodiments,the monitoring agent 197 measures and monitors the performance of anyload balancing and/or content switching 284 performed by the appliance200. In other embodiments, the monitoring agent 197 measures andmonitors the performance of application firewall 290 protection andprocessing performed by the appliance 200.

C. Client Agent

Referring now to FIG. 3, an embodiment of the client agent 120 isdepicted. The client 102 includes a client agent 120 for establishingand exchanging communications with the appliance 200 and/or server 106via a network 104. In brief overview, the client 102 operates oncomputing device 100 having an operating system with a kernel mode 302and a user mode 303, and a network stack 310 with one or more layers 310a-310 b. The client 102 may have installed and/or execute one or moreapplications. In some embodiments, one or more applications maycommunicate via the network stack 310 to a network 104. One of theapplications, such as a web browser, may also include a first program322. For example, the first program 322 may be used in some embodimentsto install and/or execute the client agent 120, or any portion thereof.The client agent 120 includes an interception mechanism, or interceptor350, for intercepting network communications from the network stack 310from the one or more applications.

The network stack 310 of the client 102 may comprise any type and formof software, or hardware, or any combinations thereof, for providingconnectivity to and communications with a network. In one embodiment,the network stack 310 comprises a software implementation for a networkprotocol suite. The network stack 310 may comprise one or more networklayers, such as any networks layers of the Open Systems Interconnection(OSI) communications model as those skilled in the art recognize andappreciate. As such, the network stack 310 may comprise any type andform of protocols for any of the following layers of the OSI model: 1)physical link layer, 2) data link layer, 3) network layer, 4) transportlayer, 5) session layer, 6) presentation layer, and 7) applicationlayer. In one embodiment, the network stack 310 may comprise a transportcontrol protocol (TCP) over the network layer protocol of the internetprotocol (IP), generally referred to as TCP/IP. In some embodiments, theTCP/IP protocol may be carried over the Ethernet protocol, which maycomprise any of the family of IEEE wide-area-network (WAN) orlocal-area-network (LAN) protocols, such as those protocols covered bythe IEEE 802.3. In some embodiments, the network stack 310 comprises anytype and form of a wireless protocol, such as IEEE 802.11 and/or mobileinternet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIFS) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 310 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 310, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 310 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 310 may be customized, modified or adapted to provide acustom or modified portion of the network stack 310 in support of any ofthe techniques described herein. In other embodiments, the accelerationprogram 302 is designed and constructed to operate with or work inconjunction with the network stack 310 installed or otherwise providedby the operating system of the client 102.

The network stack 310 comprises any type and form of interfaces forreceiving, obtaining, providing or otherwise accessing any informationand data related to network communications of the client 102. In oneembodiment, an interface to the network stack 310 comprises anapplication programming interface (API). The interface may also compriseany function call, hooking or filtering mechanism, event or call backmechanism, or any type of interfacing technique. The network stack 310via the interface may receive or provide any type and form of datastructure, such as an object, related to functionality or operation ofthe network stack 310. For example, the data structure may compriseinformation and data related to a network packet or one or more networkpackets. In some embodiments, the data structure comprises a portion ofthe network packet processed at a protocol layer of the network stack310, such as a network packet of the transport layer. In someembodiments, the data structure 325 comprises a kernel-level datastructure, while in other embodiments, the data structure 325 comprisesa user-mode data structure. A kernel-level data structure may comprise adata structure obtained or related to a portion of the network stack 310operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 310 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 310. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 310 to an application while a second portion 310 a of the networkstack 310 provides access to a network. In some embodiments, a firstportion 310 a of the network stack may comprise one or more upper layersof the network stack 310, such as any of layers 5-7. In otherembodiments, a second portion 310 b of the network stack 310 comprisesone or more lower layers, such as any of layers 1-4. Each of the firstportion 310 a and second portion 310 b of the network stack 310 maycomprise any portion of the network stack 310, at any one or morenetwork layers, in user-mode 203, kernel-mode, 202, or combinationsthereof, or at any portion of a network layer or interface point to anetwork layer or any portion of or interface point to the user-mode 203and kernel-mode 203.

The interceptor 350 may comprise software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercept a network communication at any point in the network stack 310,and redirects or transmits the network communication to a destinationdesired, managed or controlled by the interceptor 350 or client agent120. For example, the interceptor 350 may intercept a networkcommunication of a network stack 310 of a first network and transmit thenetwork communication to the appliance 200 for transmission on a secondnetwork 104. In some embodiments, the interceptor 350 comprises any typeinterceptor 350 comprises a driver, such as a network driver constructedand designed to interface and work with the network stack 310. In someembodiments, the client agent 120 and/or interceptor 350 operates at oneor more layers of the network stack 310, such as at the transport layer.In one embodiment, the interceptor 350 comprises a filter driver,hooking mechanism, or any form and type of suitable network driverinterface that interfaces to the transport layer of the network stack,such as via the transport driver interface (TDI). In some embodiments,the interceptor 350 interfaces to a first protocol layer, such as thetransport layer and another protocol layer, such as any layer above thetransport protocol layer, for example, an application protocol layer. Inone embodiment, the interceptor 350 may comprise a driver complying withthe Network Driver Interface Specification (NDIS), or a NDIS driver. Inanother embodiment, the interceptor 350 may comprise a mini-filter or amini-port driver. In one embodiment, the interceptor 350, or portionthereof, operates in kernel-mode 202. In another embodiment, theinterceptor 350, or portion thereof, operates in user-mode 203. In someembodiments, a portion of the interceptor 350 operates in kernel-mode202 while another portion of the interceptor 350 operates in user-mode203. In other embodiments, the client agent 120 operates in user-mode203 but interfaces via the interceptor 350 to a kernel-mode driver,process, service, task or portion of the operating system, such as toobtain a kernel-level data structure 225. In further embodiments, theinterceptor 350 is a user-mode application or program, such asapplication.

In one embodiment, the interceptor 350 intercepts any transport layerconnection requests. In these embodiments, the interceptor 350 executetransport layer application programming interface (API) calls to set thedestination information, such as destination IP address and/or port to adesired location for the location. In this manner, the interceptor 350intercepts and redirects the transport layer connection to a IP addressand port controlled or managed by the interceptor 350 or client agent120. In one embodiment, the interceptor 350 sets the destinationinformation for the connection to a local IP address and port of theclient 102 on which the client agent 120 is listening. For example, theclient agent 120 may comprise a proxy service listening on a local IPaddress and port for redirected transport layer communications. In someembodiments, the client agent 120 then communicates the redirectedtransport layer communication to the appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may comprise two agents120 and 120′. In one embodiment, a first agent 120 may comprise aninterceptor 350 operating at the network layer of the network stack 310.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 310. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 310 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 310 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor may operate at orinterface with the network stack 310 in a manner transparent to anyapplication, a user of the client 102, and any other computing device,such as a server, in communications with the client 102. The clientagent 120 and/or interceptor 350 may be installed and/or executed on theclient 102 in a manner without modification of an application. In someembodiments, the user of the client 102 or a computing device incommunications with the client 102 are not aware of the existence,execution or operation of the client agent 120 and/or interceptor 350.As such, in some embodiments, the client agent 120 and/or interceptor350 is installed, executed, and/or operated transparently to anapplication, user of the client 102, another computing device, such as aserver, or any of the protocol layers above and/or below the protocollayer interfaced to by the interceptor 350.

The client agent 120 includes an acceleration program 302, a streamingclient 306, a collection agent 304, and/or monitoring agent 197. In oneembodiment, the client agent 120 comprises an Independent ComputingArchitecture (ICA) client, or any portion thereof, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla., and is also referred to as anICA client. In some embodiments, the client 120 comprises an applicationstreaming client 306 for streaming an application from a server 106 to aclient 102. In some embodiments, the client agent 120 comprises anacceleration program 302 for accelerating communications between client102 and server 106. In another embodiment, the client agent 120 includesa collection agent 304 for performing end-point detection/scanning andcollecting end-point information for the appliance 200 and/or server106.

In some embodiments, the acceleration program 302 comprises aclient-side acceleration program for performing one or more accelerationtechniques to accelerate, enhance or otherwise improve a client'scommunications with and/or access to a server 106, such as accessing anapplication provided by a server 106. The logic, functions, and/oroperations of the executable instructions of the acceleration program302 may perform one or more of the following acceleration techniques: 1)multi-protocol compression, 2) transport control protocol pooling, 3)transport control protocol multiplexing, 4) transport control protocolbuffering, and 5) caching via a cache manager. Additionally, theacceleration program 302 may perform encryption and/or decryption of anycommunications received and/or transmitted by the client 102. In someembodiments, the acceleration program 302 performs one or more of theacceleration techniques in an integrated manner or fashion.Additionally, the acceleration program 302 can perform compression onany of the protocols, or multiple-protocols, carried as a payload of anetwork packet of the transport layer protocol. The streaming client 306comprises an application, program, process, service, task or executableinstructions for receiving and executing a streamed application from aserver 106. A server 106 may stream one or more application data filesto the streaming client 306 for playing, executing or otherwise causingto be executed the application on the client 102. In some embodiments,the server 106 transmits a set of compressed or packaged applicationdata files to the streaming client 306. In some embodiments, theplurality of application files are compressed and stored on a fileserver within an archive file such as a CAB, ZIP, SIT, TAR, JAR or otherarchive. In one embodiment, the server 106 decompresses, unpackages orunarchives the application files and transmits the files to the client102. In another embodiment, the client 102 decompresses, unpackages orunarchives the application files. The streaming client 306 dynamicallyinstalls the application, or portion thereof, and executes theapplication. In one embodiment, the streaming client 306 may be anexecutable program. In some embodiments, the streaming client 306 may beable to launch another executable program.

The collection agent 304 comprises an application, program, process,service, task or executable instructions for identifying, obtainingand/or collecting information about the client 102. In some embodiments,the appliance 200 transmits the collection agent 304 to the client 102or client agent 120. The collection agent 304 may be configuredaccording to one or more policies of the policy engine 236 of theappliance. In other embodiments, the collection agent 304 transmitscollected information on the client 102 to the appliance 200. In oneembodiment, the policy engine 236 of the appliance 200 uses thecollected information to determine and provide access, authenticationand authorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 comprises an end-pointdetection and scanning mechanism, which identifies and determines one ormore attributes or characteristics of the client. For example, thecollection agent 304 may identify and determine any one or more of thefollowing client-side attributes: 1) the operating system an/or aversion of an operating system, 2) a service pack of the operatingsystem, 3) a running service, 4) a running process, and 5) a file. Thecollection agent 304 may also identify and determine the presence orversions of any one or more of the following on the client: 1) antivirussoftware, 2) personal firewall software, 3) anti-spam software, and 4)internet security software. The policy engine 236 may have one or morepolicies based on any one or more of the attributes or characteristicsof the client or client-side attributes.

In some embodiments, the client agent 120 includes a monitoring agent197 as discussed in conjunction with FIGS. 1D and 2B. The monitoringagent 197 may be any type and form of script, such as Visual Basic orJava script. In one embodiment, the monitoring agent 197 monitors andmeasures performance of any portion of the client agent 120. Forexample, in some embodiments, the monitoring agent 197 monitors andmeasures performance of the acceleration program 302. In anotherembodiment, the monitoring agent 197 monitors and measures performanceof the streaming client 306. In other embodiments, the monitoring agent197 monitors and measures performance of the collection agent 304. Instill another embodiment, the monitoring agent 197 monitors and measuresperformance of the interceptor 350. In some embodiments, the monitoringagent 197 monitors and measures any resource of the client 102, such asmemory, CPU and disk.

The monitoring agent 197 may monitor and measure performance of anyapplication of the client. In one embodiment, the monitoring agent 197monitors and measures performance of a browser on the client 102. Insome embodiments, the monitoring agent 197 monitors and measuresperformance of any application delivered via the client agent 120. Inother embodiments, the monitoring agent 197 measures and monitors enduser response times for an application, such as web-based or HTTPresponse times. The monitoring agent 197 may monitor and measureperformance of an ICA or RDP client. In another embodiment, themonitoring agent 197 measures and monitors metrics for a user session orapplication session. In some embodiments, monitoring agent 197 measuresand monitors an ICA or RDP session. In one embodiment, the monitoringagent 197 measures and monitors the performance of the appliance 200 inaccelerating delivery of an application and/or data to the client 102.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or portionthereof, such as the interceptor 350, automatically, silently,transparently, or otherwise. In one embodiment, the first program 322comprises a plugin component, such an ActiveX control or Java control orscript that is loaded into and executed by an application. For example,the first program comprises an ActiveX control loaded and run by a webbrowser application, such as in the memory space or context of theapplication. In another embodiment, the first program 322 comprises aset of executable instructions loaded into and run by the application,such as a browser. In one embodiment, the first program 322 comprises adesigned and constructed program to install the client agent 120. Insome embodiments, the first program 322 obtains, downloads, or receivesthe client agent 120 via the network from another computing device. Inanother embodiment, the first program 322 is an installer program or aplug and play manager for installing programs, such as network drivers,on the operating system of the client 102.

D. Systems and Methods for Providing Virtualized Application DeliveryController

Referring now to FIG. 4A, a block diagram depicts one embodiment of avirtualization environment 400. In brief overview, a computing device100 includes a hypervisor layer, a virtualization layer, and a hardwarelayer. The hypervisor layer includes a hypervisor 401 (also referred toas a virtualization manager) that allocates and manages access to anumber of physical resources in the hardware layer (e.g., theprocessor(s) 421, and disk(s) 428) by at least one virtual machineexecuting in the virtualization layer. The virtualization layer includesat least one operating system 410 and a plurality of virtual resourcesallocated to the at least one operating system 410. Virtual resourcesmay include, without limitation, a plurality of virtual processors 432a, 432 b, 432 c (generally 432), and virtual disks 442 a, 442 b, 442 c(generally 442), as well as virtual resources such as virtual memory andvirtual network interfaces. The plurality of virtual resources and theoperating system 410 may be referred to as a virtual machine 406. Avirtual machine 406 may include a control operating system 405 incommunication with the hypervisor 401 and used to execute applicationsfor managing and configuring other virtual machines on the computingdevice 100.

In greater detail, a hypervisor 401 may provide virtual resources to anoperating system in any manner which simulates the operating systemhaving access to a physical device. A hypervisor 401 may provide virtualresources to any number of guest operating systems 410 a, 410 b(generally 410). In some embodiments, a computing device 100 executesone or more types of hypervisors. In these embodiments, hypervisors maybe used to emulate virtual hardware, partition physical hardware,virtualize physical hardware, and execute virtual machines that provideaccess to computing environments. Hypervisors may include thosemanufactured by VMWare, Inc., of Palo Alto, Calif.; the XEN hypervisor,an open source product whose development is overseen by the open sourceXen.org community; HyperV, VirtualServer or virtual PC hypervisorsprovided by Microsoft, or others. In some embodiments, a computingdevice 100 executing a hypervisor that creates a virtual machineplatform on which guest operating systems may execute is referred to asa host server. In one of these embodiments, for example, the computingdevice 100 is a XEN SERVER provided by Citrix Systems, Inc., of FortLauderdale, Fla.

In some embodiments, a hypervisor 401 executes within an operatingsystem executing on a computing device. In one of these embodiments, acomputing device executing an operating system and a hypervisor 401 maybe said to have a host operating system (the operating system executingon the computing device), and a guest operating system (an operatingsystem executing within a computing resource partition provided by thehypervisor 401). In other embodiments, a hypervisor 401 interactsdirectly with hardware on a computing device, instead of executing on ahost operating system. In one of these embodiments, the hypervisor 401may be said to be executing on “bare metal,” referring to the hardwarecomprising the computing device.

In some embodiments, a hypervisor 401 may create a virtual machine 406a-c (generally 406) in which an operating system 410 executes. In one ofthese embodiments, for example, the hypervisor 401 loads a virtualmachine image to create a virtual machine 406. In another of theseembodiments, the hypervisor 401 executes an operating system 410 withinthe virtual machine 406. In still another of these embodiments, thevirtual machine 406 executes an operating system 410.

In some embodiments, the hypervisor 401 controls processor schedulingand memory partitioning for a virtual machine 406 executing on thecomputing device 100. In one of these embodiments, the hypervisor 401controls the execution of at least one virtual machine 406. In anotherof these embodiments, the hypervisor 401 presents at least one virtualmachine 406 with an abstraction of at least one hardware resourceprovided by the computing device 100. In other embodiments, thehypervisor 401 controls whether and how physical processor capabilitiesare presented to the virtual machine 406.

A control operating system 405 may execute at least one application formanaging and configuring the guest operating systems. In one embodiment,the control operating system 405 may execute an administrativeapplication, such as an application including a user interface providingadministrators with access to functionality for managing the executionof a virtual machine, including functionality for executing a virtualmachine, terminating an execution of a virtual machine, or identifying atype of physical resource for allocation to the virtual machine. Inanother embodiment, the hypervisor 401 executes the control operatingsystem 405 within a virtual machine 406 created by the hypervisor 401.In still another embodiment, the control operating system 405 executesin a virtual machine 406 that is authorized to directly access physicalresources on the computing device 100. In some embodiments, a controloperating system 405 a on a computing device 100 a may exchange datawith a control operating system 405 b on a computing device 100 b, viacommunications between a hypervisor 401 a and a hypervisor 401 b. Inthis way, one or more computing devices 100 may exchange data with oneor more of the other computing devices 100 regarding processors andother physical resources available in a pool of resources. In one ofthese embodiments, this functionality allows a hypervisor to manage apool of resources distributed across a plurality of physical computingdevices. In another of these embodiments, multiple hypervisors manageone or more of the guest operating systems executed on one of thecomputing devices 100.

In one embodiment, the control operating system 405 executes in avirtual machine 406 that is authorized to interact with at least oneguest operating system 410. In another embodiment, a guest operatingsystem 410 communicates with the control operating system 405 via thehypervisor 401 in order to request access to a disk or a network. Instill another embodiment, the guest operating system 410 and the controloperating system 405 may communicate via a communication channelestablished by the hypervisor 401, such as, for example, via a pluralityof shared memory pages made available by the hypervisor 401.

In some embodiments, the control operating system 405 includes a networkback-end driver for communicating directly with networking hardwareprovided by the computing device 100. In one of these embodiments, thenetwork back-end driver processes at least one virtual machine requestfrom at least one guest operating system 110. In other embodiments, thecontrol operating system 405 includes a block back-end driver forcommunicating with a storage element on the computing device 100. In oneof these embodiments, the block back-end driver reads and writes datafrom the storage element based upon at least one request received from aguest operating system 410.

In one embodiment, the control operating system 405 includes a toolsstack 404. In another embodiment, a tools stack 404 providesfunctionality for interacting with the hypervisor 401, communicatingwith other control operating systems 405 (for example, on a secondcomputing device 100 b), or managing virtual machines 406 b, 406 c onthe computing device 100. In another embodiment, the tools stack 404includes customized applications for providing improved managementfunctionality to an administrator of a virtual machine farm. In someembodiments, at least one of the tools stack 404 and the controloperating system 405 include a management API that provides an interfacefor remotely configuring and controlling virtual machines 406 running ona computing device 100. In other embodiments, the control operatingsystem 405 communicates with the hypervisor 401 through the tools stack404.

In one embodiment, the hypervisor 401 executes a guest operating system410 within a virtual machine 406 created by the hypervisor 401. Inanother embodiment, the guest operating system 410 provides a user ofthe computing device 100 with access to resources within a computingenvironment. In still another embodiment, a resource includes a program,an application, a document, a file, a plurality of applications, aplurality of files, an executable program file, a desktop environment, acomputing environment, or other resource made available to a user of thecomputing device 100. In yet another embodiment, the resource may bedelivered to the computing device 100 via a plurality of access methodsincluding, but not limited to, conventional installation directly on thecomputing device 100, delivery to the computing device 100 via a methodfor application streaming, delivery to the computing device 100 ofoutput data generated by an execution of the resource on a secondcomputing device 100′ and communicated to the computing device 100 via apresentation layer protocol, delivery to the computing device 100 ofoutput data generated by an execution of the resource via a virtualmachine executing on a second computing device 100′, or execution from aremovable storage device connected to the computing device 100, such asa USB device, or via a virtual machine executing on the computing device100 and generating output data. In some embodiments, the computingdevice 100 transmits output data generated by the execution of theresource to another computing device 100′.

In one embodiment, the guest operating system 410, in conjunction withthe virtual machine on which it executes, forms a fully-virtualizedvirtual machine which is not aware that it is a virtual machine; such amachine may be referred to as a “Domain U HVM (Hardware Virtual Machine)virtual machine”. In another embodiment, a fully-virtualized machineincludes software emulating a Basic Input/Output System (BIOS) in orderto execute an operating system within the fully-virtualized machine. Instill another embodiment, a fully-virtualized machine may include adriver that provides functionality by communicating with the hypervisor401. In such an embodiment, the driver may be aware that it executeswithin a virtualized environment. In another embodiment, the guestoperating system 410, in conjunction with the virtual machine on whichit executes, forms a paravirtualized virtual machine, which is awarethat it is a virtual machine; such a machine may be referred to as a“Domain U PV virtual machine”. In another embodiment, a paravirtualizedmachine includes additional drivers that a fully-virtualized machinedoes not include. In still another embodiment, the paravirtualizedmachine includes the network back-end driver and the block back-enddriver included in a control operating system 405, as described above.

Referring now to FIG. 4B, a block diagram depicts one embodiment of aplurality of networked computing devices in a system in which at leastone physical host executes a virtual machine. In brief overview, thesystem includes a management component 404 and a hypervisor 401. Thesystem includes a plurality of computing devices 100, a plurality ofvirtual machines 406, a plurality of hypervisors 401, a plurality ofmanagement components referred to variously as tools stacks 404 ormanagement components 404, and a physical resource 421, 428. Theplurality of physical machines 100 may each be provided as computingdevices 100, described above in connection with FIGS. 1E-1H and 4A.

In greater detail, a physical disk 428 is provided by a computing device100 and stores at least a portion of a virtual disk 442. In someembodiments, a virtual disk 442 is associated with a plurality ofphysical disks 428. In one of these embodiments, one or more computingdevices 100 may exchange data with one or more of the other computingdevices 100 regarding processors and other physical resources availablein a pool of resources, allowing a hypervisor to manage a pool ofresources distributed across a plurality of physical computing devices.In some embodiments, a computing device 100 on which a virtual machine406 executes is referred to as a physical host 100 or as a host machine100.

The hypervisor executes on a processor on the computing device 100. Thehypervisor allocates, to a virtual disk, an amount of access to thephysical disk. In one embodiment, the hypervisor 401 allocates an amountof space on the physical disk. In another embodiment, the hypervisor 401allocates a plurality of pages on the physical disk. In someembodiments, the hypervisor provisions the virtual disk 442 as part of aprocess of initializing and executing a virtual machine 450.

In one embodiment, the management component 404 a is referred to as apool management component 404 a. In another embodiment, a managementoperating system 405 a, which may be referred to as a control operatingsystem 405 a, includes the management component. In some embodiments,the management component is referred to as a tools stack. In one ofthese embodiments, the management component is the tools stack 404described above in connection with FIG. 4A. In other embodiments, themanagement component 404 provides a user interface for receiving, from auser such as an administrator, an identification of a virtual machine406 to provision and/or execute. In still other embodiments, themanagement component 404 provides a user interface for receiving, from auser such as an administrator, the request for migration of a virtualmachine 406 b from one physical machine 100 to another. In furtherembodiments, the management component 404 a identifies a computingdevice 100 b on which to execute a requested virtual machine 406 d andinstructs the hypervisor 401 b on the identified computing device 100 bto execute the identified virtual machine; such a management componentmay be referred to as a pool management component.

Referring now to FIG. 4C, embodiments of a virtual application deliverycontroller or virtual appliance 450 are depicted. In brief overview, anyof the functionality and/or embodiments of the appliance 200 (e.g., anapplication delivery controller) described above in connection withFIGS. 2A and 2B may be deployed in any embodiment of the virtualizedenvironment described above in connection with FIGS. 4A and 4B. Insteadof the functionality of the application delivery controller beingdeployed in the form of an appliance 200, such functionality may bedeployed in a virtualized environment 400 on any computing device 100,such as a client 102, server 106 or appliance 200.

Referring now to FIG. 4C, a diagram of an embodiment of a virtualappliance 450 operating on a hypervisor 401 of a server 106 is depicted.As with the appliance 200 of FIGS. 2A and 2B, the virtual appliance 450may provide functionality for availability, performance, offload andsecurity. For availability, the virtual appliance may perform loadbalancing between layers 4 and 7 of the network and may also performintelligent service health monitoring. For performance increases vianetwork traffic acceleration, the virtual appliance may perform cachingand compression. To offload processing of any servers, the virtualappliance may perform connection multiplexing and pooling and/or SSLprocessing. For security, the virtual appliance may perform any of theapplication firewall functionality and SSL VPN function of appliance200.

Any of the modules of the appliance 200 as described in connection withFIG. 2A may be packaged, combined, designed or constructed in a form ofthe virtualized appliance delivery controller 450 deployable as one ormore software modules or components executable in a virtualizedenvironment 300 or non-virtualized environment on any server, such as anoff the shelf server. For example, the virtual appliance may be providedin the form of an installation package to install on a computing device.With reference to FIG. 2A, any of the cache manager 232, policy engine236, compression 238, encryption engine 234, packet engine 240, GUI 210,CLI 212, shell services 214 and health monitoring programs 216 may bedesigned and constructed as a software component or module to run on anyoperating system of a computing device and/or of a virtualizedenvironment 300. Instead of using the encryption processor 260,processor 262, memory 264 and network stack 267 of the appliance 200,the virtualized appliance 400 may use any of these resources as providedby the virtualized environment 400 or as otherwise available on theserver 106.

Still referring to FIG. 4C, and in brief overview, any one or morevServers 275A-275N may be in operation or executed in a virtualizedenvironment 400 of any type of computing device 100, such as any server106. Any of the modules or functionality of the appliance 200 describedin connection with FIG. 2B may be designed and constructed to operate ineither a virtualized or non-virtualized environment of a server. Any ofthe vServer 275, SSL VPN 280, Intranet UP 282, Switching 284, DNS 286,acceleration 288, App FW 280 and monitoring agent may be packaged,combined, designed or constructed in a form of application deliverycontroller 450 deployable as one or more software modules or componentsexecutable on a device and/or virtualized environment 400.

In some embodiments, a server may execute multiple virtual machines 406a-406 n in the virtualization environment with each virtual machinerunning the same or different embodiments of the virtual applicationdelivery controller 450. In some embodiments, the server may execute oneor more virtual appliances 450 on one or more virtual machines on a coreof a multi-core processing system. In some embodiments, the server mayexecute one or more virtual appliances 450 on one or more virtualmachines on each processor of a multiple processor device.

E. Systems and Methods for Providing A Multi-Core Architecture

In accordance with Moore's Law, the number of transistors that may beplaced on an integrated circuit may double approximately every twoyears. However, CPU speed increases may reach plateaus, for example CPUspeed has been around 3.5-4 GHz range since 2005. In some cases, CPUmanufacturers may not rely on CPU speed increases to gain additionalperformance. Some CPU manufacturers may add additional cores to theirprocessors to provide additional performance. Products, such as those ofsoftware and networking vendors, that rely on CPUs for performance gainsmay improve their performance by leveraging these multi-core CPUs. Thesoftware designed and constructed for a single CPU may be redesignedand/or rewritten to take advantage of a multi-threaded, parallelarchitecture or otherwise a multi-core architecture.

A multi-core architecture of the appliance 200, referred to as nCore ormulti-core technology, allows the appliance in some embodiments to breakthe single core performance barrier and to leverage the power ofmulti-core CPUs. In the previous architecture described in connectionwith FIG. 2A, a single network or packet engine is run. The multiplecores of the nCore technology and architecture allow multiple packetengines to run concurrently and/or in parallel. With a packet enginerunning on each core, the appliance architecture leverages theprocessing capacity of additional cores. In some embodiments, thisprovides up to a 7× increase in performance and scalability.

Illustrated in FIG. 5A are some embodiments of work, task, load ornetwork traffic distribution across one or more processor coresaccording to a type of parallelism or parallel computing scheme, such asfunctional parallelism, data parallelism or flow-based data parallelism.In brief overview, FIG. 5A illustrates embodiments of a multi-coresystem such as an appliance 200′ with n-cores, a total of cores numbers1 through N. In one embodiment, work, load or network traffic can bedistributed among a first core 505A, a second core 505B, a third core505C, a fourth core 505D, a fifth core 505E, a sixth core 505F, aseventh core 505G, and so on such that distribution is across all or twoor more of the n cores 505N (hereinafter referred to collectively ascores 505.) There may be multiple VIPs 275 each running on a respectivecore of the plurality of cores. There may be multiple packet engines 240each running on a respective core of the plurality of cores. Any of theapproaches used may lead to different, varying or similar work load orperformance level 515 across any of the cores. For a functionalparallelism approach, each core may run a different function of thefunctionalities provided by the packet engine, a VIP 275 or appliance200. In a data parallelism approach, data may be paralleled ordistributed across the cores based on the Network Interface Card (NIC)or VIP 275 receiving the data. In another data parallelism approach,processing may be distributed across the cores by distributing dataflows to each core.

In further detail to FIG. 5A, in some embodiments, load, work or networktraffic can be distributed among cores 505 according to functionalparallelism 500. Functional parallelism may be based on each coreperforming one or more respective functions. In some embodiments, afirst core may perform a first function while a second core performs asecond function. In functional parallelism approach, the functions to beperformed by the multi-core system are divided and distributed to eachcore according to functionality. In some embodiments, functionalparallelism may be referred to as task parallelism and may be achievedwhen each processor or core executes a different process or function onthe same or different data. The core or processor may execute the sameor different code. In some cases, different execution threads or codemay communicate with one another as they work. Communication may takeplace to pass data from one thread to the next as part of a workflow.

In some embodiments, distributing work across the cores 505 according tofunctional parallelism 500, can comprise distributing network trafficaccording to a particular function such as network input/outputmanagement (NW I/O) 510A, secure sockets layer (SSL) encryption anddecryption 510B and transmission control protocol (TCP) functions 510C.This may lead to a work, performance or computing load 515 based on avolume or level of functionality being used. In some embodiments,distributing work across the cores 505 according to data parallelism540, can comprise distributing an amount of work 515 based ondistributing data associated with a particular hardware or softwarecomponent. In some embodiments, distributing work across the cores 505according to flow-based data parallelism 520, can comprise distributingdata based on a context or flow such that the amount of work 515A-N oneach core may be similar, substantially equal or relatively evenlydistributed.

In the case of the functional parallelism approach, each core may beconfigured to run one or more functionalities of the plurality offunctionalities provided by the packet engine or VIP of the appliance.For example, core 1 may perform network I/O processing for the appliance200′ while core 2 performs TCP connection management for the appliance.Likewise, core 3 may perform SSL offloading while core 4 may performlayer 7 or application layer processing and traffic management. Each ofthe cores may perform the same function or different functions. Each ofthe cores may perform more than one function. Any of the cores may runany of the functionality or portions thereof identified and/or describedin conjunction with FIGS. 2A and 2B. In this the approach, the workacross the cores may be divided by function in either a coarse-grainedor fine-grained manner. In some cases, as illustrated in FIG. 5A,division by function may lead to different cores running at differentlevels of performance or load 515.

In the case of the functional parallelism approach, each core may beconfigured to run one or more functionalities of the plurality offunctionalities provided by the packet engine of the appliance. Forexample, core 1 may perform network I/O processing for the appliance200′ while core 2 performs TCP connection management for the appliance.Likewise, core 3 may perform SSL offloading while core 4 may performlayer 7 or application layer processing and traffic management. Each ofthe cores may perform the same function or different functions. Each ofthe cores may perform more than one function. Any of the cores may runany of the functionality or portions thereof identified and/or describedin conjunction with FIGS. 2A and 2B. In this the approach, the workacross the cores may be divided by function in either a coarse-grainedor fine-grained manner. In some cases, as illustrated in FIG. 5Adivision by function may lead to different cores running at differentlevels of load or performance.

The functionality or tasks may be distributed in any arrangement andscheme. For example, FIG. 5B illustrates a first core, Core 1 505A,processing applications and processes associated with network I/Ofunctionality 510A. Network traffic associated with network I/O, in someembodiments, can be associated with a particular port number. Thus,outgoing and incoming packets having a port destination associated withNW PO 510A will be directed towards Core 1 505A which is dedicated tohandling all network traffic associated with the NW I/O port. Similarly,Core 2 505B is dedicated to handling functionality associated with SSLprocessing and Core 4 505D may be dedicated handling all TCP levelprocessing and functionality.

While FIG. 5A illustrates functions such as network I/O, SSL and TCP,other functions can be assigned to cores. These other functions caninclude any one or more of the functions or operations described herein.For example, any of the functions described in conjunction with FIGS. 2Aand 2B may be distributed across the cores on a functionality basis. Insome cases, a first VIP 275A may run on a first core while a second VIP275B with a different configuration may run on a second core. In someembodiments, each core 505 can handle a particular functionality suchthat each core 505 can handle the processing associated with thatparticular function. For example, Core 2 505B may handle SSL offloadingwhile Core 4 505D may handle application layer processing and trafficmanagement.

In other embodiments, work, load or network traffic may be distributedamong cores 505 according to any type and form of data parallelism 540.In some embodiments, data parallelism may be achieved in a multi-coresystem by each core performing the same task or functionally ondifferent pieces of distributed data. In some embodiments, a singleexecution thread or code controls operations on all pieces of data. Inother embodiments, different threads or instructions control theoperation, but may execute the same code. In some embodiments, dataparallelism is achieved from the perspective of a packet engine,vServers (VIPs) 275A-C, network interface cards (NIC) 542D-E and/or anyother networking hardware or software included on or associated with anappliance 200. For example, each core may run the same packet engine orVIP code or configuration but operate on different sets of distributeddata. Each networking hardware or software construct can receivedifferent, varying or substantially the same amount of data, and as aresult may have varying, different or relatively the same amount of load515.

In the case of a data parallelism approach, the work may be divided upand distributed based on VIPs, NICs and/or data flows of the VIPs orNICs. In one of these approaches, the work of the multi-core system maybe divided or distributed among the VIPs by having each VIP work on adistributed set of data. For example, each core may be configured to runone or more VIPs. Network traffic may be distributed to the core foreach VIP handling that traffic. In another of these approaches, the workof the appliance may be divided or distributed among the cores based onwhich NIC receives the network traffic. For example, network traffic ofa first NIC may be distributed to a first core while network traffic ofa second NIC may be distributed to a second core. In some cases, a coremay process data from multiple NICs.

While FIG. 5A illustrates a single vServer associated with a single core505, as is the case for VIP1 275A, VIP2 275B and VIP3 275C. In someembodiments, a single vServer can be associated with one or more cores505. In contrast, one or more vServers can be associated with a singlecore 505. Associating a vServer with a core 505 may include that core505 to process all functions associated with that particular vServer. Insome embodiments, each core executes a VIP having the same code andconfiguration. In other embodiments, each core executes a VIP having thesame code but different configuration. In some embodiments, each coreexecutes a VIP having different code and the same or differentconfiguration.

Like vServers, NICs can also be associated with particular cores 505. Inmany embodiments, NICs can be connected to one or more cores 505 suchthat when a NIC receives or transmits data packets, a particular core505 handles the processing involved with receiving and transmitting thedata packets. In one embodiment, a single NIC can be associated with asingle core 505, as is the case with NIC1 542D and NIC2 542E. In otherembodiments, one or more NICs can be associated with a single core 505.In other embodiments, a single NIC can be associated with one or morecores 505. In these embodiments, load could be distributed amongst theone or more cores 505 such that each core 505 processes a substantiallysimilar amount of load. A core 505 associated with a NIC may process allfunctions and/or data associated with that particular NIC.

While distributing work across cores based on data of VIPs or NICs mayhave a level of independency, in some embodiments, this may lead tounbalanced use of cores as illustrated by the varying loads 515 of FIG.5A.

In some embodiments, load, work or network traffic can be distributedamong cores 505 based on any type and form of data flow. In another ofthese approaches, the work may be divided or distributed among coresbased on data flows. For example, network traffic between a client and aserver traversing the appliance may be distributed to and processed byone core of the plurality of cores. In some cases, the core initiallyestablishing the session or connection may be the core for which networktraffic for that session or connection is distributed. In someembodiments, the data flow is based on any unit or portion of networktraffic, such as a transaction, a request/response communication ortraffic originating from an application on a client. In this manner andin some embodiments, data flows between clients and servers traversingthe appliance 200′ may be distributed in a more balanced manner than theother approaches.

In flow-based data parallelism 520, distribution of data is related toany type of flow of data, such as request/response pairings,transactions, sessions, connections or application communications. Forexample, network traffic between a client and a server traversing theappliance may be distributed to and processed by one core of theplurality of cores. In some cases, the core initially establishing thesession or connection may be the core for which network traffic for thatsession or connection is distributed. The distribution of data flow maybe such that each core 505 carries a substantially equal or relativelyevenly distributed amount of load, data or network traffic.

In some embodiments, the data flow is based on any unit or portion ofnetwork traffic, such as a transaction, a request/response communicationor traffic originating from an application on a client. In this mannerand in some embodiments, data flows between clients and serverstraversing the appliance 200′ may be distributed in a more balancedmanner than the other approached. In one embodiment, data flow can bedistributed based on a transaction or a series of transactions. Thistransaction, in some embodiments, can be between a client and a serverand can be characterized by an IP address or other packet identifier.For example, Core 1 505A can be dedicated to transactions between aparticular client and a particular server, therefore the load 515A onCore 1 505A may be comprised of the network traffic associated with thetransactions between the particular client and server. Allocating thenetwork traffic to Core 1 505A can be accomplished by routing all datapackets originating from either the particular client or server to Core1 505A.

While work or load can be distributed to the cores based in part ontransactions, in other embodiments load or work can be allocated on aper packet basis. In these embodiments, the appliance 200 can interceptdata packets and allocate them to a core 505 having the least amount ofload. For example, the appliance 200 could allocate a first incomingdata packet to Core 1 505A because the load 515A on Core 1 is less thanthe load 515B-N on the rest of the cores 505B-N. Once the first datapacket is allocated to Core 1 505A, the amount of load 515A on Core 1505A is increased proportional to the amount of processing resourcesneeded to process the first data packet. When the appliance 200intercepts a second data packet, the appliance 200 will allocate theload to Core 4 505D because Core 4 505D has the second least amount ofload. Allocating data packets to the core with the least amount of loadcan, in some embodiments, ensure that the load 515A-N distributed toeach core 505 remains substantially equal.

In other embodiments, load can be allocated on a per unit basis where asection of network traffic is allocated to a particular core 505. Theabove-mentioned example illustrates load balancing on a per/packetbasis. In other embodiments, load can be allocated based on a number ofpackets such that every 10, 100 or 1000 packets are allocated to thecore 505 having the least amount of load. The number of packetsallocated to a core 505 can be a number determined by an application,user or administrator and can be any number greater than zero. In stillother embodiments, load can be allocated based on a time metric suchthat packets are distributed to a particular core 505 for apredetermined amount of time. In these embodiments, packets can bedistributed to a particular core 505 for five milliseconds or for anyperiod of time determined by a user, program, system, administrator orotherwise. After the predetermined time period elapses, data packets aretransmitted to a different core 505 for the predetermined period oftime.

Flow-based data parallelism methods for distributing work, load ornetwork traffic among the one or more cores 505 can comprise anycombination of the above-mentioned embodiments. These methods can becarried out by any part of the appliance 200, by an application or setof executable instructions executing on one of the cores 505, such asthe packet engine, or by any application, program or agent executing ona computing device in communication with the appliance 200.

The functional and data parallelism computing schemes illustrated inFIG. 5A can be combined in any manner to generate a hybrid parallelismor distributed processing scheme that encompasses function parallelism500, data parallelism 540, flow-based data parallelism 520 or anyportions thereof. In some cases, the multi-core system may use any typeand form of load balancing schemes to distribute load among the one ormore cores 505. The load balancing scheme may be used in any combinationwith any of the functional and data parallelism schemes or combinationsthereof.

Illustrated in FIG. 5B is an embodiment of a multi-core system 545,which may be any type and form of one or more systems, appliances,devices or components. This system 545, in some embodiments, can beincluded within an appliance 200 having one or more processing cores505A-N. The system 545 can further include one or more packet engines(PE) or packet processing engines (PPE) 548A-N communicating with amemory bus 556. The memory bus may be used to communicate with the oneor more processing cores 505A-N. Also included within the system 545 canbe one or more network interface cards (NIC) 552 and a flow distributor550 which can further communicate with the one or more processing cores505A-N. The flow distributor 550 can comprise a Receive Side Scaler(RSS) or Receive Side Scaling (RSS) module 560.

Further referring to FIG. 5B, and in more detail, in one embodiment thepacket engine(s) 548A-N can comprise any portion of the appliance 200described herein, such as any portion of the appliance described inFIGS. 2A and 2B. The packet engine(s) 548A-N can, in some embodiments,comprise any of the following elements: the packet engine 240, a networkstack 267; a cache manager 232; a policy engine 236; a compressionengine 238; an encryption engine 234; a GUI 210; a CLI 212; shellservices 214; monitoring programs 216; and any other software orhardware element able to receive data packets from one of either thememory bus 556 or the one of more cores 505A-N. In some embodiments, thepacket engine(s) 548A-N can comprise one or more vServers 275A-N, or anyportion thereof. In other embodiments, the packet engine(s) 548A-N canprovide any combination of the following functionalities: SSL VPN 280;Intranet UP 282; switching 284; DNS 286; packet acceleration 288; App FW280; monitoring such as the monitoring provided by a monitoring agent197; functionalities associated with functioning as a TCP stack; loadbalancing; SSL offloading and processing; content switching; policyevaluation; caching; compression; encoding; decompression; decoding;application firewall functionalities; XML processing and acceleration;and SSL VPN connectivity.

The packet engine(s) 548A-N can, in some embodiments, be associated witha particular server, user, client or network. When a packet engine 548becomes associated with a particular entity, that packet engine 548 canprocess data packets associated with that entity. For example, should apacket engine 548 be associated with a first user, that packet engine548 will process and operate on packets generated by the first user, orpackets having a destination address associated with the first user.Similarly, the packet engine 548 may choose not to be associated with aparticular entity such that the packet engine 548 can process andotherwise operate on any data packets not generated by that entity ordestined for that entity.

In some instances, the packet engine(s) 548A-N can be configured tocarry out the any of the functional and/or data parallelism schemesillustrated in FIG. 5A. In these instances, the packet engine(s) 548A-Ncan distribute functions or data among the processing cores 505A-N sothat the distribution is according to the parallelism or distributionscheme. In some embodiments, a single packet engine(s) 548A-N carriesout a load balancing scheme, while in other embodiments one or morepacket engine(s) 548A-N carry out a load balancing scheme. Each core505A-N, in one embodiment, can be associated with a particular packetengine 548 such that load balancing can be carried out by the packetengine. Load balancing may in this embodiment, provide that each packetengine 548A-N associated with a core 505 communicate with the otherpacket engines associated with cores so that the packet engines 548A-Ncan collectively determine where to distribute load. One embodiment ofthis process can include an arbiter that receives votes from each packetengine for load. The arbiter can distribute load to each packet engine548A-N based in part on the age of the engine's vote and in some cases apriority value associated with the current amount of load on an engine'sassociated core 505.

Any of the packet engines running on the cores may run in user mode,kernel or any combination thereof. In some embodiments, the packetengine operates as an application or program running is user orapplication space. In these embodiments, the packet engine may use anytype and form of interface to access any functionality provided by thekernel. In some embodiments, the packet engine operates in kernel modeor as part of the kernel. In some embodiments, a first portion of thepacket engine operates in user mode while a second portion of the packetengine operates in kernel mode. In some embodiments, a first packetengine on a first core executes in kernel mode while a second packetengine on a second core executes in user mode. In some embodiments, thepacket engine or any portions thereof operates on or in conjunction withthe NIC or any drivers thereof.

In some embodiments the memory bus 556 can be any type and form ofmemory or computer bus. While a single memory bus 556 is depicted inFIG. 5B, the system 545 can comprise any number of memory buses 556. Inone embodiment, each packet engine 548 can be associated with one ormore individual memory buses 556.

The NIC 552 can in some embodiments be any of the network interfacecards or mechanisms described herein. The NIC 552 can have any number ofports. The NIC can be designed and constructed to connect to any typeand form of network 104. While a single NIC 552 is illustrated, thesystem 545 can comprise any number of NICs 552. In some embodiments,each core 505A-N can be associated with one or more single NICs 552.Thus, each core 505 can be associated with a single NIC 552 dedicated toa particular core 505.

The cores 505A-N can comprise any of the processors described herein.Further, the cores 505A-N can be configured according to any of the core505 configurations described herein. Still further, the cores 505A-N canhave any of the core 505 functionalities described herein. While FIG. 5Billustrates seven cores 505A-G, any number of cores 505 can be includedwithin the system 545. In particular, the system 545 can comprise “N”cores, where “N” is a whole number greater than zero.

A core may have or use memory that is allocated or assigned for use tothat core. The memory may be considered private or local memory of thatcore and only accessible by that core. A core may have or use memorythat is shared or assigned to multiple cores. The memory may beconsidered public or shared memory that is accessible by more than onecore. A core may use any combination of private and public memory. Withseparate address spaces for each core, some level of coordination iseliminated from the case of using the same address space. With aseparate address space, a core can perform work on information and datain the core's own address space without worrying about conflicts withother cores. Each packet engine may have a separate memory pool for TCPand/or SSL connections.

Further referring to FIG. 5B, any of the functionality and/orembodiments of the cores 505 described above in connection with FIG. 5Acan be deployed in any embodiment of the virtualized environmentdescribed above in connection with FIGS. 4A and 4B. Instead of thefunctionality of the cores 505 being deployed in the form of a physicalprocessor 505, such functionality may be deployed in a virtualizedenvironment 400 on any computing device 100, such as a client 102,server 106 or appliance 200. In other embodiments, instead of thefunctionality of the cores 505 being deployed in the form of anappliance or a single device, the functionality may be deployed acrossmultiple devices in any arrangement. For example, one device maycomprise two or more cores and another device may comprise two or morecores. For example, a multi-core system may include a cluster ofcomputing devices, a server farm or network of computing devices. Insome embodiments, instead of the functionality of the cores 505 beingdeployed in the form of cores, the functionality may be deployed on aplurality of processors, such as a plurality of single core processors.

In one embodiment, the cores 505 may be any type and form of processor.In some embodiments, a core can function substantially similar to anyprocessor or central processing unit described herein. In someembodiment, the cores 505 may comprise any portion of any processordescribed herein. While FIG. 5A illustrates seven cores, there can existany “N” number of cores within an appliance 200, where “N” is any wholenumber greater than one. In some embodiments, the cores 505 can beinstalled within a common appliance 200, while in other embodiments thecores 505 can be installed within one or more appliance(s) 200communicatively connected to one another. The cores 505 can in someembodiments comprise graphics processing software, while in otherembodiments the cores 505 provide general processing capabilities. Thecores 505 can be installed physically near each other and/or can becommunicatively connected to each other. The cores may be connected byany type and form of bus or subsystem physically and/or communicativelycoupled to the cores for transferring data between to, from and/orbetween the cores.

While each core 505 can comprise software for communicating with othercores, in some embodiments a core manager (not shown) can facilitatecommunication between each core 505. In some embodiments, the kernel mayprovide core management. The cores may interface or communicate witheach other using a variety of interface mechanisms. In some embodiments,core to core messaging may be used to communicate between cores, such asa first core sending a message or data to a second core via a bus orsubsystem connecting the cores. In some embodiments, cores maycommunicate via any type and form of shared memory interface. In oneembodiment, there may be one or more memory locations shared among allthe cores. In some embodiments, each core may have separate memorylocations shared with each other core. For example, a first core mayhave a first shared memory with a second core and a second share memorywith a third core. In some embodiments, cores may communicate via anytype of programming or API, such as function calls via the kernel. Insome embodiments, the operating system may recognize and supportmultiple core devices and provide interfaces and API for inter-corecommunications.

The flow distributor 550 can be any application, program, library,script, task, service, process or any type and form of executableinstructions executing on any type and form of hardware. In someembodiments, the flow distributor 550 may any design and construction ofcircuitry to perform any of the operations and functions describedherein. In some embodiments, the flow distributor distribute, forwards,routes, controls and/or manage the distribution of data packets amongthe cores 505 and/or packet engine or VIPs running on the cores. Theflow distributor 550, in some embodiments, can be referred to as aninterface master. In one embodiment, the flow distributor 550 comprisesa set of executable instructions executing on a core or processor of theappliance 200. In another embodiment, the flow distributor 550 comprisesa set of executable instructions executing on a computing machine incommunication with the appliance 200. In some embodiments, the flowdistributor 550 comprises a set of executable instructions executing ona NIC, such as firmware. In still other embodiments, the flowdistributor 550 comprises any combination of software and hardware todistribute data packets among cores or processors. In one embodiment,the flow distributor 550 executes on at least one of the cores 505A-N,while in other embodiments a separate flow distributor 550 assigned toeach core 505A-N executes on an associated core 505A-N. The flowdistributor may use any type and form of statistical or probabilisticalgorithms or decision making to balance the flows across the cores. Thehardware of the appliance, such as a NIC, or the kernel may be designedand constructed to support sequential operations across the NICs and/orcores.

In embodiments where the system 545 comprises one or more flowdistributors 550, each flow distributor 550 can be associated with aprocessor 505 or a packet engine 548. The flow distributors 550 cancomprise an interface mechanism that allows each flow distributor 550 tocommunicate with the other flow distributors 550 executing within thesystem 545. In one instance, the one or more flow distributors 550 candetermine how to balance load by communicating with each other. Thisprocess can operate substantially similarly to the process describedabove for submitting votes to an arbiter which then determines whichflow distributor 550 should receive the load. In other embodiments, afirst flow distributor 550′ can identify the load on an associated coreand determine whether to forward a first data packet to the associatedcore based on any of the following criteria: the load on the associatedcore is above a predetermined threshold; the load on the associated coreis below a predetermined threshold; the load on the associated core isless than the load on the other cores; or any other metric that can beused to determine where to forward data packets based in part on theamount of load on a processor.

The flow distributor 550 can distribute network traffic among the cores505 according to a distribution, computing or load balancing scheme suchas those described herein. In one embodiment, the flow distributor candistribute network traffic according to any one of a functionalparallelism distribution scheme 550, a data parallelism loaddistribution scheme 540, a flow-based data parallelism distributionscheme 520, or any combination of these distribution scheme or any loadbalancing scheme for distributing load among multiple processors. Theflow distributor 550 can therefore act as a load distributor by takingin data packets and distributing them across the processors according toan operative load balancing or distribution scheme. In one embodiment,the flow distributor 550 can comprise one or more operations, functionsor logic to determine how to distribute packers, work or loadaccordingly. In still other embodiments, the flow distributor 550 cancomprise one or more sub operations, functions or logic that canidentify a source address and a destination address associated with adata packet, and distribute packets accordingly.

In some embodiments, the flow distributor 550 can comprise areceive-side scaling (RSS) network driver, module 560 or any type andform of executable instructions which distribute data packets among theone or more cores 505. The RSS module 560 can comprise any combinationof hardware and software. In some embodiments, the RSS module 560 worksin conjunction with the flow distributor 550 to distribute data packetsacross the cores 505A-N or among multiple processors in amulti-processor network. The RSS module 560 can execute within the NIC552 in some embodiments, and in other embodiments can execute on any oneof the cores 505.

In some embodiments, the RSS module 560 uses the MICROSOFTreceive-side-scaling (RSS) scheme. In one embodiment, RSS is a MicrosoftScalable Networking initiative technology that enables receiveprocessing to be balanced across multiple processors in the system whilemaintaining in-order delivery of the data. The RSS may use any type andform of hashing scheme to determine a core or processor for processing anetwork packet.

The RSS module 560 can apply any type and form hash function such as theToeplitz hash function. The hash function may be applied to the hashtype or any the sequence of values. The hash function may be a securehash of any security level or is otherwise cryptographically secure. Thehash function may use a hash key. The size of the key is dependent uponthe hash function. For the Toeplitz hash, the size may be 40 bytes forIPv6 and 16 bytes for IPv4.

The hash function may be designed and constructed based on any one ormore criteria or design goals. In some embodiments, a hash function maybe used that provides an even distribution of hash result for differenthash inputs and different hash types, including TCP/IPv4, TCP/IPv6,IPv4, and IPv6 headers. In some embodiments, a hash function may be usedthat provides a hash result that is evenly distributed when a smallnumber of buckets are present (for example, two or four). In someembodiments, hash function may be used that provides a hash result thatis randomly distributed when a large number of buckets were present (forexample, 64 buckets). In some embodiments, the hash function isdetermined based on a level of computational or resource usage. In someembodiments, the hash function is determined based on ease or difficultyof implementing the hash in hardware. In some embodiments, the hashfunction is determined based on the ease or difficulty of a maliciousremote host to send packets that would all hash to the same bucket.

The RSS may generate hashes from any type and form of input, such as asequence of values. This sequence of values can include any portion ofthe network packet, such as any header, field or payload of networkpacket, or portions thereof. In some embodiments, the input to the hashmay be referred to as a hash type and include any tuples of informationassociated with a network packet or data flow, such as any of thefollowing: a four tuple comprising at least two IP addresses and twoports; a four tuple comprising any four sets of values; a six tuple; atwo tuple; and/or any other sequence of numbers or values. The followingare example of hash types that may be used by RSS:

-   -   4-tuple of source TCP Port, source IP version 4 (IPv4) address,        destination TCP Port, and destination IPv4 address.    -   4-tuple of source TCP Port, source IP version 6 (IPv6) address,        destination TCP Port, and destination IPv6 address.    -   2-tuple of source IPv4 address, and destination IPv4 address.    -   2-tuple of source IPv6 address, and destination IPv6 address.    -   2-tuple of source IPv6 address, and destination IPv6 address,        including support for parsing IPv6 extension headers.

The hash result or any portion thereof may used to identify a core orentity, such as a packet engine or VIP, for distributing a networkpacket. In some embodiments, one or more hash bits or mask are appliedto the hash result. The hash bit or mask may be any number of bits orbytes. A NIC may support any number of bits, such as seven bits. Thenetwork stack may set the actual number of bits to be used duringinitialization. The number will be between 1 and 7, inclusive.

The hash result may be used to identify the core or entity via any typeand form of table, such as a bucket table or indirection table. In someembodiments, the number of hash-result bits are used to index into thetable. The range of the hash mask may effectively define the size of theindirection table. Any portion of the hash result or the hash resultitself may be used to index the indirection table. The values in thetable may identify any of the cores or processor, such as by a core orprocessor identifier. In some embodiments, all of the cores of themulti-core system are identified in the table. In other embodiments, aport of the cores of the multi-core system are identified in the table.The indirection table may comprise any number of buckets for example 2to 128 buckets that may be indexed by a hash mask. Each bucket maycomprise a range of index values that identify a core or processor. Insome embodiments, the flow controller and/or RSS module may rebalancethe network rebalance the network load by changing the indirectiontable.

In some embodiments, the multi-core system 575 does not include a RSSdriver or RSS module 560. In some of these embodiments, a softwaresteering module (not shown) or a software embodiment of the RSS modulewithin the system can operate in conjunction with or as part of the flowdistributor 550 to steer packets to cores 505 within the multi-coresystem 575.

The flow distributor 550, in some embodiments, executes within anymodule or program on the appliance 200, on any one of the cores 505 andon any one of the devices or components included within the multi-coresystem 575. In some embodiments, the flow distributor 550′ can executeon the first core 505A, while in other embodiments the flow distributor550″ can execute on the NIC 552. In still other embodiments, an instanceof the flow distributor 550′ can execute on each core 505 included inthe multi-core system 575. In this embodiment, each instance of the flowdistributor 550′ can communicate with other instances of the flowdistributor 550′ to forward packets back and forth across the cores 505.There exist situations where a response to a request packet may not beprocessed by the same core, i.e. the first core processes the requestwhile the second core processes the response. In these situations, theinstances of the flow distributor 550′ can intercept the packet andforward it to the desired or correct core 505, i.e. a flow distributorinstance 550′ can forward the response to the first core. Multipleinstances of the flow distributor 550′ can execute on any number ofcores 505 and any combination of cores 505.

The flow distributor may operate responsive to any one or more rules orpolicies. The rules may identify a core or packet processing engine toreceive a network packet, data or data flow. The rules may identify anytype and form of tuple information related to a network packet, such asa 4-tuple of source and destination IP address and source anddestination ports. Based on a received packet matching the tuplespecified by the rule, the flow distributor may forward the packet to acore or packet engine. In some embodiments, the packet is forwarded to acore via shared memory and/or core to core messaging.

Although FIG. 5B illustrates the flow distributor 550 as executingwithin the multi-core system 575, in some embodiments the flowdistributor 550 can execute on a computing device or appliance remotelylocated from the multi-core system 575. In such an embodiment, the flowdistributor 550 can communicate with the multi-core system 575 to takein data packets and distribute the packets across the one or more cores505. The flow distributor 550 can, in one embodiment, receive datapackets destined for the appliance 200, apply a distribution scheme tothe received data packets and distribute the data packets to the one ormore cores 505 of the multi-core system 575. In one embodiment, the flowdistributor 550 can be included in a router or other appliance such thatthe router can target particular cores 505 by altering meta dataassociated with each packet so that each packet is targeted towards asub-node of the multi-core system 575. In such an embodiment, CISCO'svn-tag mechanism can be used to alter or tag each packet with theappropriate meta data.

Illustrated in FIG. 5C is an embodiment of a multi-core system 575comprising one or more processing cores 505A-N. In brief overview, oneof the cores 505 can be designated as a control core 505A and can beused as a control plane 570 for the other cores 505. The other cores maybe secondary cores which operate in a data plane while the control coreprovides the control plane. The cores 505A-N may share a global cache580. While the control core provides a control plane, the other cores inthe multi-core system form or provide a data plane. These cores performdata processing functionality on network traffic while the controlprovides initialization, configuration and control of the multi-coresystem.

Further referring to FIG. 5C, and in more detail, the cores 505A-N aswell as the control core 505A can be any processor described herein.Furthermore, the cores 505A-N and the control core 505A can be anyprocessor able to function within the system 575 described in FIG. 5C.Still further, the cores 505A-N and the control core 505A can be anycore or group of cores described herein. The control core may be adifferent type of core or processor than the other cores. In someembodiments, the control may operate a different packet engine or have apacket engine configured differently than the packet engines of theother cores.

Any portion of the memory of each of the cores may be allocated to orused for a global cache that is shared by the cores. In brief overview,a predetermined percentage or predetermined amount of each of the memoryof each core may be used for the global cache. For example, 50% of eachmemory of each code may be dedicated or allocated to the shared globalcache. That is, in the illustrated embodiment, 2 GB of each coreexcluding the control plane core or core 1 may be used to form a 28 GBshared global cache. The configuration of the control plane such as viathe configuration services may determine the amount of memory used forthe shared global cache. In some embodiments, each core may provide adifferent amount of memory for use by the global cache. In otherembodiments, any one core may not provide any memory or use the globalcache. In some embodiments, any of the cores may also have a local cachein memory not allocated to the global shared memory. Each of the coresmay store any portion of network traffic to the global shared cache.Each of the cores may check the cache for any content to use in arequest or response. Any of the cores may obtain content from the globalshared cache to use in a data flow, request or response.

The global cache 580 can be any type and form of memory or storageelement, such as any memory or storage element described herein. In someembodiments, the cores 505 may have access to a predetermined amount ofmemory (i.e. 32 GB or any other memory amount commensurate with thesystem 575). The global cache 580 can be allocated from thatpredetermined amount of memory while the rest of the available memorycan be allocated among the cores 505. In other embodiments, each core505 can have a predetermined amount of memory. The global cache 580 cancomprise an amount of the memory allocated to each core 505. This memoryamount can be measured in bytes, or can be measured as a percentage ofthe memory allocated to each core 505. Thus, the global cache 580 cancomprise 1 GB of memory from the memory associated with each core 505,or can comprise 20 percent or one-half of the memory associated witheach core 505. In some embodiments, only a portion of the cores 505provide memory to the global cache 580, while in other embodiments theglobal cache 580 can comprise memory not allocated to the cores 505.

Each core 505 can use the global cache 580 to store network traffic orcache data. In some embodiments, the packet engines of the core use theglobal cache to cache and use data stored by the plurality of packetengines. For example, the cache manager of FIG. 2A and cachefunctionality of FIG. 2B may use the global cache to share data foracceleration. For example, each of the packet engines may storeresponses, such as HTML data, to the global cache. Any of the cachemanagers operating on a core may access the global cache to servercaches responses to client requests.

In some embodiments, the cores 505 can use the global cache 580 to storea port allocation table which can be used to determine data flow basedin part on ports. In other embodiments, the cores 505 can use the globalcache 580 to store an address lookup table or any other table or listthat can be used by the flow distributor to determine where to directincoming and outgoing data packets. The cores 505 can, in someembodiments read from and write to cache 580, while in other embodimentsthe cores 505 can only read from or write to cache 580. The cores mayuse the global cache to perform core to core communications.

The global cache 580 may be sectioned into individual memory sectionswhere each section can be dedicated to a particular core 505. In oneembodiment, the control core 505A can receive a greater amount ofavailable cache, while the other cores 505 can receiving varying amountsor access to the global cache 580.

In some embodiments, the system 575 can comprise a control core 505A.While FIG. 5C illustrates core 1 505A as the control core, the controlcore can be any core within the appliance 200 or multi-core system.Further, while only a single control core is depicted, the system 575can comprise one or more control cores each having a level of controlover the system. In some embodiments, one or more control cores can eachcontrol a particular aspect of the system 575. For example, one core cancontrol deciding which distribution scheme to use, while another corecan determine the size of the global cache 580.

The control plane of the multi-core system may be the designation andconfiguration of a core as the dedicated management core or as a mastercore. This control plane core may provide control, management andcoordination of operation and functionality the plurality of cores inthe multi-core system. This control plane core may provide control,management and coordination of allocation and use of memory of thesystem among the plurality of cores in the multi-core system, includinginitialization and configuration of the same. In some embodiments, thecontrol plane includes the flow distributor for controlling theassignment of data flows to cores and the distribution of networkpackets to cores based on data flows. In some embodiments, the controlplane core runs a packet engine and in other embodiments, the controlplane core is dedicated to management and control of the other cores ofthe system.

The control core 505A can exercise a level of control over the othercores 505 such as determining how much memory should be allocated toeach core 505 or determining which core 505 should be assigned to handlea particular function or hardware/software entity. The control core505A, in some embodiments, can exercise control over those cores 505within the control plan 570. Thus, there can exist processors outside ofthe control plane 570 which are not controlled by the control core 505A.Determining the boundaries of the control plane 570 can includemaintaining, by the control core 505A or agent executing within thesystem 575, a list of those cores 505 controlled by the control core505A. The control core 505A can control any of the following:initialization of a core; determining when a core is unavailable;re-distributing load to other cores 505 when one core fails; determiningwhich distribution scheme to implement; determining which core shouldreceive network traffic; determining how much cache should be allocatedto each core; determining whether to assign a particular function orelement to a particular core; determining whether to permit cores tocommunicate with one another; determining the size of the global cache580; and any other determination of a function, configuration oroperation of the cores within the system 575.

F. Systems and Methods for Managing SSL Session Persistence and Reuse

A SSL session may be allocated private memory address space andassociated with a SSL protocol stack that is independent from other SSLsessions. In a single-core system such as a single-core appliance 200maintaining a SSL session between a client 102 and a server 106, the SSLsession may be resumed if the SSL session is temporarily disruptedand/or inactive. For example, a disruption may occur due to a mobileclient disconnecting and reconnecting to a network 104, or a servergoing offline due to inactivity or power loss. A client may send arequest to resume the SSL session instead of establishing a new session.This may be more efficient in terms of the time and resources consumedin performing a full handshake process, allocating memory, starting aprotocol stack and meeting authentication/authorization requirements.Furthermore, the disrupted SSL session may remain persistent although aconnection may be lost. Resuming a SSL session may also maintain somelevel of continuity in client-server communications.

In some embodiments, a packet engine 240 maintains a connection betweena client 102 and a core 661, directing packets from the client 102 tothe core 661. The packet engine 240 can maintain a TCP connectionthrough a core, for example, by identifying the core based oninformation from received packets and/or client 102. A flow distributor550 may direct traffic to a packet engine 240 of a core by associating aconnection based on information from received packets and/or client 102.In one embodiment, this information includes a TCP tuple or TCPquadruple. A TCP tuple may include information on a source IP address, asource port number, a destination IP address and a destination portnumber. The TCP tuple may be extracted from a packet. The TCP tuple mayremain the same for a client connection and/or session. In someembodiments, a disruption to a connection of session may cause the TCPtuple to change. For example, the source port number may change if theclient attempts to reconnect to the intermediary 200.

The flow distributor 550 may generate a hash index or other identifierbased on a TCP tuple to associate the packet traffic with a core. Insome embodiments, when a TCP tuple changes, a different hash index oridentifier is generated and a second core 662 is identified instead.Upon a disruption to a connection or session, a client 102 may attemptto resume transmission of packets. These packets may come from adifferent application instance of the client 102. These packets mayprovide different source port information. Other components of the TCPtuple may also change. Based on a changed TCP tuple, the flowdistributor may generate a second hash index or identifier and directpacket traffic from the client 102 to a second core 662 corresponding tothe second hash index or identifier.

In some embodiments, use of a flow distributor 550 and/or packet enginesin a multi-core system can result in higher SSL transactions per second(TPS) and/or bulk throughput numbers. Each core may have a virtual IPaddress (VIP) associated with the core that may or may not beestablished in relation to a SSL session 641. In some embodiments, theflow distributor 550 identifies each core via the VIP of the core.

Referring now to FIG. 6, an embodiment of a system 600 for managing SSLsession persistence and reuse is depicted. In brief overview, the systemincludes an intermediary 200 between a client 102 and a server 106. Theintermediary 200 comprises a multi-core system, a flow distributor 550,and a storage or memory module 667. In some embodiments, a SSL session641 may be established and maintained by one of a plurality of cores ina multi-core system, such as the first core 661. This core 661 issometimes referred to as the owner of the SSL session 641. Upondisruption of the SSL session 641, a client 102 may request resumptionof the SSL session by sending a request 672 to the multi-core system.The flow distributor 550 may direct the request 672 to a second core 662that will determine if it owns the disrupted SSL session 641. The secondcore 662 may identify the owner 661 of the session 641 and determine ifthe session can be resumed. The second core 662 can communicate with thefirst core 661 and receive information for cloning the disrupted SSLsession for reuse by the second core 662. Upon completion of thecloning, the connection between the client and the server is resumedbased on the cloned session 641′.

Each core 661, 662 of the multi-core system can include a transceiver621, 622. The transceiver can receive packets or messages directed fromthe flow distributor 550. The transceiver can also communicate withother cores of the multi-core system. In some embodiments, inter-corecommunication involves sending a core-to-core messaging (CCM) messagefrom a first core 661 to a second core 662. The transceiver may supportpackets and messages based on any type or form of communicationprotocols. The transceiver can also communicate with other components ofthe intermediary 200. For example, a core can access data from memory667 using the transceiver as an interface. The transceiver can alsotransmit a packet or message to another machine such as server 106. Thetransceiver may direct outgoing packets or messages to a destinationbased on information from the associated TCP tuple.

Each core may include a decoder-encoder pair 631, 632 (hereinaftergenerally referred to as a “cipher”). A cipher may comprise hardware orany combination of software and hardware. The cipher may include anapplication, program, library, script, process, task, thread or any typeand form of executable instructions. Although the cipher is illustratedas part of a certificate manager, in some embodiments, the cipher may bea separate component or module of the multi-core system. In oneembodiment, the cipher may include a general-purpose encoder/decoder. Inanother embodiment, the cipher is designed and constructed toencode/encrypt or decode/decrypt any type and form of information, suchas session identifiers 688 and/or core identifiers 656, 658. In oneembodiment, the ciphers 631, 632 are block ciphers. Further, the ciphersmay include functionality from any embodiment of the encryption engine234 described in connection with FIG. 2. In some embodiments, the system600 uses data encryption standard (DES) ciphers, such as standard DESciphers and 3DES ciphers.

The first core 661 is assigned a core identifier 656. The coreidentifier 656 may be any type or form of alphanumeric identifier orcode string. In addition, this core identifier 656 may be unique amongthe plurality of cores of the multi-core system. The core identifier 656may be a CPU number of the core 661, or incorporate the CPU number ofthe core 661. A core identifier 656 may be assigned sequentially to eachcore based on the CPU numbers of the cores. The core identifier 656 canbe of any size. In one embodiment, the core identifier 656 is one bytein size. In particular, one byte can give 256 (0-255) unique coreidentifiers.

The first core 661 can establish a SSL session 641 between the client102 and the server 106. The SSL session 641 may be established inconnection with the cipher 631 and/or functionality from any embodimentof the encryption engine 234 described in connection with FIG. 2. TheSSL session 641 is assigned a session identifier 688 which can be anytype or form of alphanumeric identifier or code string. The first core661, the backend server 106 or the client 102 may issue the sessionidentifier 688. The session identifier 668 may uniquely identify the SSLsession among a plurality of SSL sessions associated with the multi-coresystem. A session identifier 688 may be a random 16 or 32 byte value. Inone embodiment, the X-OR of the byte[0] with byte[1] location of thesession identifier 688 results in a random value. By randomly selectinga one-byte location in the session identifier 688 for encoding the coreidentifier 656, such as at system boot time, additional security andrandomness with respect to the session identifier 688 may beincorporated. In one embodiment, a SSLv2 session identifier 688 has asize of 16 bytes and the last 4 bytes may contain a time-stamp. In thisembodiment, the one-byte location for the core identifier 656 ispreferably between byte 0 to byte 11. In another embodiment, a sessionidentifier 688 is 32 bytes for SSLv3 and TLSv1. The lower 4 bytes may betaken up by the timestamp, allowing 28 bytes for encoding a coreidentifier in SSLv3/TLSv1 protocol. Other than the byte locationsreserved for timestamp purposes, the byte location for encoding a coreidentifier may be selected by any means.

By way of illustration and not limiting in any way, one embodiment ofpseudo code for encoding a core identifier may be:

sessionid[0] = coreid; sessionid[0] {circumflex over ( )}= sessionid[1];and one embodiment of pseudo code for retrieving the core identifier maybe:

coreid = sessionid[0] {circumflex over ( )} sessionid[1];

In some embodiments, a valid-session identifier is encoded with a coreidentifier. A valid-session identifier is sometimes referred to as avalidity identifier. A valid-session identifier can be a string thatidentifies a valid session. As an example, a cipher may use 8 bytes toencode the valid-session identifier and the core identifier. Theintermediary 200 or the multi-core system can determine whether asession 641 is valid. In one embodiment, use of a valid-sessionidentifier helps to filter away random or malicious requests to reuse asession. A valid-session identifier may also identify active reusedsessions.

In some other embodiments, the core identifier 656 is not encoded withina byte or a range of bits of a session identifier. Instead, individualbits of a session identifier 688 can be used to encode a core identifier656. The core identifier 656 can be encoded as a bit pattern in thesession identifier 688. Other than the byte locations that are reservedfor timestamp purposes, the individual bit locations for encoding a coreidentifier 656 may be selected by any means. When a session identifier688 is generated by the core 661 owning the SSL session 641, individualbits can be set to encode the core identifier 656. The number of bitsthat are set or unset may depend on the number of cores in themulti-core system. This method may impose a relatively small footprinton session identifiers as the number of bits affected is limited to thenumber of cores in the multi-core system.

The first core 661 or the packet engine 240 of the first core 661 maystore the session identifier 688 in a session cache of the first core661. In one embodiment, the session cache 651 is persistent for theduration that the core 661 is powered up and/or the duration that asession 641 is maintained. In another embodiment, the session cache 651is persistent even when the core 6671 is powered down, or when a session641 has ended. The session cache 651 can be memory allocated to thefirst core 661 and/or the SSL session 641. The session cache 651 may beaccessed by one or more cores. In some embodiments, the first core 661maintains and/or updates the session cache 651. The memory module 667may include the session cache 651. The memory module 667 may compriseone or more interconnected storage devices, such as any embodiment ofstorage devices 128, 140, 122, 264, 667 described above in connectionwith FIGS. 1E, 1F and 2A.

In some embodiments, the session cache 651 stores the session identifier688 of the SSL session 641 established by the first core 661. Thesession cache 651 may store a plurality of session identifiers, such assession identifiers of sessions established by the first core 661. Thefirst core 661 may encode the core identifier 656 in the sessionidentifier 688 to form a second session identifier 688′. In someembodiments, the cipher 631 encodes the core identifier 656 in thesession identifier 688 to form the second session identifier 688′. Inone embodiment, the cipher 631 encodes the core identifier 656 in onebyte of the session identifier 688. Encoder/decoder routines of thecipher 631 can securely encode the core identifier 656 in the secondsession identifier 688′ and/or decode the core identifier 656.Encoder/decoder routines of the cipher 631 can also securelyencode/decode a valid-session-identifier in association with the sessionidentifier 688. In another embodiment, the core identifier 656 can bedirectly stored into bits of the second session identifier 688′. Thesecond session identifier 688′ can be stored in the session cache 651either with the session identifier 688 or in replacement of the sessionidentifier 688.

In some embodiments, the second core 662 is substantially similar oridentical to the first core 661 in terms of functionality, capabilityand/or associated elements. For example, the second core includes atransceiver 622 and a decoder 632, and is associated with a sessioncache 652. The second core 662 can be assigned a unique core identifier658. The second may similarly establish a new SSL session. In addition,the second core 662 may reuse a SSL session 641 of the first core 661.

The intermediary 200 includes a set of policies 657. These policies 657may be any embodiments of the policies described in connection withFIGS. 1D, 2A, 2B and 3. These policies 657 may be applied to a request,such as a request 672 to resume a SSL session. The policies 657 can alsodetermine to which core the flow distributor 500 directs an incomingmessage. In addition, an associated policy engine may apply the policies657, for example, to determine whether a session can be resumed orreused. In some embodiments, the policies 657 are stored in the memorymodule 667. For example, the policies can be stored in a privatepartition of the memory module 667. Some of these policies 656 may begrouped and associated with a client 102 and/or a server 106.

A core may resume a session that it has established. For example, a coremay resume a session that it has established by restarting part of theprotocol stack of the session that was disrupted. A core may resume asession that was established by another core, by creating a copy orclone of the session in the core. In some embodiments, the latter caseis referred to as a reuse of the session. In these embodiments, resuminga session may have a broader scope than reusing a session. In otherembodiments, session resume or reuse can be used interchangeably. Instill other embodiments, reuse refers to the reuse of some elements of asession, such as security parameters of the session.

Each SSL session may be associated with a resumable indicator 668. Theresumable indicator 668 may be predetermined or dynamically updated. Anadministrator, the server 106 or a core 661 establishing a SSL session641 may determine and/or set an associated resumable indicator 668. Theresumable indicator 668 may be determined and/or set via analysis ofsession history and/or statistics, such as via any algorithm or processsteps. In other embodiments, a core 662 reusing the SSL session 641 maybe able to update the resumable indicator 668 of the SSL session 641. Insome other embodiments, a core 662 reusing the SSL session 641 may sendinformation to the owner 661 of the SSL session 641 to update theresumable indicator 668 of the SSL session 641.

The resumable indicator 668 may indicate whether a request 672 to resumea SSL session should be allowed. The resumable indicator 668 mayindicate whether a request to resume a SSL session 641 is allowedsubject to a reuse limit 678 and/or other factors. A resumable indicator668 may be set based on the state of the SSL session, for example,whether the session is active and/or is being reused by one or morecores. In one embodiment, the resumable indicator 668 may be set asnon-resumable when the SSL session 641 is still active. In anotherembodiment, the resumable indicator 668 may be set as resumable if aninactive SSL session 641 has not expired and/or is not corrupted. In oneembodiment, if a fatal alert is sent or received in a SSL session 641,the corresponding resumable indicator 668 is set as non-resumable. Insome embodiments, if the resumable indicator 668 is set asnon-resumable, all further session resume requests may be rejected ordiscarded.

A second core 662 processing a request 672 to reuse and/or resume a SSLsession 641 may access the resumable indicator 668 to determine whetherthe SSL session 641 is resumable. The resumable indicator 668 may bestored at a shared location in memory 667 accessible by a plurality ofcores. The resumable indicator 668 may also be stored at a location inmemory 667 accessible by each core of the multi-core system. In someembodiments, the resumable indicator 668 of a SSL session established bya core can be stored in the session cache 651 of that core and/or thatsession. The resumable indicator 668 may be stored in a location inshared memory. The resumable indicator 668 may be one byte in sizealthough other embodiments are supported. In some embodiments, thestored value is a pointer to a larger memory location. In otherembodiments, a plurality of cores (e.g., cores requesting reuse of theSSL session 641) can each store a copy of the resumable indicator 668.In one of these embodiments, the plurality of cores having a copy of theresumable indicator 668 may check for updates to the resumable indicator668, or receive a notification of an update to the resumable indicator668. An update or notification may be sent as a CCM message from thefirst core 661. An update or notification may be sent to coresidentified to be reusing the SSL session 641.

In some embodiments, the packet engine 240 stores a reuse limit 678 to amemory module 667. A reuse limit 678 is sometimes referred to as amaximum reuse threshold. This reuse limit 678 may indicate the number oftimes a session can be resumed or reused. This reuse limit 678 may bepredetermined or dynamically updated. The reuse limit 678 may bedetermined and set by an administrator and/or via analysis of sessionhistory and/or statistics, such as via any algorithm or process steps.The first core 661 may specify a reuse limit 678 a directed to the firstcore 661, to the multi-core system, or to the SSL session 641established by the first core 661. A second core 662 reusing a SSLsession 641 owned by the first core 661 may specify a reuse limit 678 bdirected to the second core 662. The reuse limit 678 of a session for acore can be stored in the session cache 651 of that core and/or thatsession. The reuse limit 678 may also be stored in a shared location inmemory 667 accessible by a plurality of cores. The reuse limit 678 of acore may also be stored in memory partitioned or allocated for a core.In some embodiments, a reuse limit 678 may be set to limit the reuse ofa session that may be inherently unstable or prone to disruption. Inother embodiments, a reuse limit 678 may be set to limit cumulativeand/or parallel reuse of a SSL session by a plurality of cores.

In some embodiments, if the resumable indicator 668 for a sessionindicates that that the session is non-resumable, reuse of the sessionis not allowed. In one of these embodiments, the reuse limit 668 isremoved. In another of these embodiments, the reuse limit 668 is set tozero. A core attempting to process a request 672 to reuse and/or resumea SSL session 641 may access the reuse limit 678 to determine whetherthe SSL session is reusable. If the resumable indicator 668 for asession indicates that that the session is resumable and the reuse limit678 of a core and/or session is not reached, reuse of the session may beallowed. In some embodiments, the reuse limit 678 and the resumableindicator 668 are determined and/or set independently. In otherembodiments, the reuse limit 678 and the resumable indicator 668 aredetermined and/or set in relation to each another. In some otherembodiments, the reuse limit 678 and/or the resumable indicator 668 aredetermined in accordance with other factors such whether the session hasexpired and/or is corrupted.

To resume a SSL session 641, a client may send a request 672 to theintermediary 200. The flow distributor 550 of the intermediary 200 canprocess the request 672 and/or forward the request to one of theplurality of cores. The request 672 may include a session identifier 688of the SSL session 641 identified to resume. The request 672 may alsoinclude any information related to the session 641, the client 102, theserver 106 and the first core 661. If a second core 662 receives therequest, the second core 662 may send a message to the first core 661requesting for information about the SSL session 641. The second core662 can use this information about the SSL session 641 to copy, clone,reconstruct, duplicate, mirror or otherwise create a SSL session 641′substantially similar to the original SSL session 641. This process maybe generally referred to as cloning a session. The SSL session 641′ issometimes referred to as a copy of the original session 641, or a cloneof the original session 641.

The information about the SSL session 641 may include one or more of:protocol stack information, TCP tuple information, a master key, aclient certificate, a name of a cipher, a result of clientauthentication, and an SSL version. Some or all of these information maybe held in the SSL session data structure of the SSL session 641. Thesecond core 662 may access some or all of these information via thefirst core 661. Although information for generating an identical SSLsession may be available in the session data structure of the SSLsession 641, a complete copy of the session data structure may not berequired to clone and resume the SSL session.

In some embodiments, protocol stack information may be determined fromthe SSL version information. In other embodiments, information on thestate and/or components of the protocol stack, such as that of driversand agents that may be dynamically installed and/or configured, can beused for cloning the SSL session 641. The first core 661 may use atleast some portions of TCP tuple information to clone the SSL session641. The first core 661 may also obtain TCP tuple information from therequest 672.

A first core 661 or a packet processor 240 of the core can use a masterkey for the SSL session to manage security, for example data encryptionand decryption, and securing transactions though authorization andauthentication. The master key can be applied to SSL certificates. Themaster key can be 48 bits long although other embodiments are alsosupported. In some embodiments, the master key can be a FederalInformation Processing Standard (FIPS) key, such as one generated by aFIPS card. The intermediary 200 may include a FIPS card in communicationwith the first core 661. The master key can also be created by acertificate authority (CA), such as a local CA residing in theintermediary 200. In one embodiment, the CA executes on the first core661 and generates certificates, certificate revocation lists (CRLs) andcertificate signing requests (CSRs) in addition to the keys. By way ofillustration and not limiting in any way, one embodiment of a set oftypical commands for a CA is as follows:

create ssl rsakey

convert ssl pkcs12

convert ssl pkcs8

create ssl dhParam

create ssl dsaKey

create ssl crl

create ssl certReq

create ssl cert

The second core 662 may request some or all of the generated informationfrom the first core 661 to clone the SSL session 641. In someembodiments, the second core 662 requests a minimum set of informationto reuse the SSL session 641. The first core 661 may send a minimal setof information to the second core 662 to clone the SSL session 641. Thefirst core 661 may send one or more messages containing the set ofinformation to clone the SSL session 641.

The first core 661 can use information related to the clientcertificate, for example, to determine the certificate authority status,issuer identifier of the certificate, and whether the certificate isvalid and/or revoked. Client certificate information can facilitateauthentication and/or authorization management in the cloned session. Insome embodiments, a client certificate is used to support clientauthentication and/or SSL data insertion. In different embodiments,client certificate information can be of variable size.

The name or type of a cipher, including any configuration of the cipher,can allow the second core 662 to decode/encode/decrypt/encrypt dataconsistent with the SSL session 641. Cipher information can be sent in32 bytes of information, although other embodiments can be supported. Inaddition, client authentication results can facilitate re-authenticationof the client and/or allow bypass of some authentication steps. Clientauthentication results may also be used in policy-based authenticationof the client 102, such as using one or more of the policies 656. Clientauthentication results can be sent in 4 bytes of information, althoughother embodiments can be supported.

The second core 662 may also request for the SSL version to clone a SSLnetwork protocol stack and/or session data structure. The SSL versionmay also facilitate cloning of connections within the SSL networkprotocol stack as well as connections between any layer of the protocolstack with the client 102, server 106, and any other network component.SSL version information can be sent in 4 bytes of information, althoughother embodiments can be supported. In some embodiments, additionalinformation or arguments for using the master key and/or other keys canbe used to clone a SSL session. For example and in one embodiment, SSLv2protocol may use a 8 bit key argument.

The first core 661 that owns the SSL session 641 may store informationabout session reuse by other cores. This information can be maintainedas a bit-pattern, such as a bit pattern representing the cores of themulti-core system, in the session cache 651 or in memory 667. Thisinformation may also include a reference count of cloned sessions 641′.This information can be used for ageing the cloned sessions for timeout.On timeout of a cloned session 641′, the non-owner core (for example,the second core 662) may send a message to the first core 661 indicatingthat the cloned session 641′ has ended. In response to this message, thefirst core 661 may update the stored information, e.g., a referencecount of cloned sessions. In one embodiment, the SSL session 641 may notbe terminated if cloned sessions are active. In some embodiments, eachcore processes session ageing irrespective of whether the SSL session isa cloned or original session. Certain operations performed by a coredescribed herein in various embodiments may be performed by a packetengine 240 of the core.

Referring now to FIGS. 7A and 7B, a flow diagram depicting an embodimentof steps of a method 700 for maintaining session persistence and reusein a multi-core system is shown. In brief overview, at step 701, a firstcore of a multi-core system in an intermediary 200 receives a request671 from a client 102 to establish a secure socket layer (SSL) session641 with a server 106, the core 661 assigned a first core identifier656. At step 703, the first core 661 establishes a session identifierfor the SSL session 641. At step 705, the first core encodes the firstcore identifier 656 in the session identifier to form a second sessionidentifier 688. At step 707, the first core 661 establishes the SSLsession 641 with the client 102 using the second session identifier 688.At step 709, the first core 661 stores the second session identifier 688in a session cache 651 of the first core 661. At step 711, the firstcore 661 indicates whether the SSL session 641 is resumable. At step713, the first core 661 sets an indicator 668 at a location in memory667 accessible by each core of the multi-core system, the indicator 668indicating whether the SSL session 641 is resumable. At step 715, a flowdistributor 550 of the multi-core system forwards a second request 672from the client 102 to a second core 662 to reuse and resume the SSLsession 641. At step 717, the second core 662 receives the secondrequest 672 from the client 102, the request 672 comprising the secondsession identifier 688. The second core 662 is assigned a second coreidentifier 658. At step 719, the second core 662 determines that thesecond session identifier 688 is not in a session cache 652 of thesecond core 662.

At step 721, the second core 662 decodes a core identifier 656 encodedin the second session identifier 688. At step 723, the second core 662determines whether the indicator 668 in the memory location indicatesthat the SSL session 641 is resumable. At step 725, the second core 662determines whether a reuse limit 678 for the SSL session 641 has beenexceeded. At step 727, the second core 662 determines whether the coreidentifier 658 corresponds to the second core identifier 658. At step729, the second core 662 resumes client communications with the server106 in the SSL session 641′. At step 731, the second core 662 forwardsthe request 672 to the server 106. At step 733, the second core 662transmits a message requesting information about the SSL session 641 tothe first core 661 identified by the core identifier 656. At step 735,the first core 661 identifies the second core 662 via a second coreidentifier 658 included in the message received from the second core662. At step 737, the first core 661 transmits a message to the secondcore 662. At step 739, the first core 661 transmits to the second core662 the message indicating that the SSL session 641 is not reusable. Atstep 741, the second core 662 determines not to resume the SSL session641 based on at least one of: the message from the first core, theidentification that the second core is not the establisher of the SSLsession 641, application of a policy, the indicator 668, and the reuselimit 678. At step 743, the first core 661 transmits, to the second core662, at least one of: a master key, a client certificate, a name of acipher 631, a result of client authentication, and an SSL version in themessage. At step 745, the second core 662 establishes a copy of the SSLsession 641′ on the second core 662 based on the information about theSSL session 641 obtained from the first core 661. At step 747, thesecond core 662 resumes client communications with the server 106 in thecopy of the SSL session 641′.

In further details of step 701, a first core of a multi-core system inan intermediary receives a request from a client to establish a SSLsession with a server. In one embodiment, a first core 661 of multi-coresystem deployed as an intermediary 200 between the client 102 and aserver 106 receives a request 671 from a client 102 to establish a SSLsession 641 with a server 106. In some embodiments, the first core 661receives a client-hello message 671 from the client 102. The first core661 may receive a first request 671 from the client 102 via the flowdistributor 550. The first core 661 is assigned a first core identifier656. The first core 661 may be assigned a core identifier 656 based onan identifier of a processing unit of the first core. In one embodiment,the first core 661 is assigned a one-byte core identifier 656. Themulti-core system, the flow distributor 550, or other component of theintermediary 200 may generate and assign the first core identifier 656to the first core 661. The first core identifier 656 may be generatedvia application of at least one policy 657.

The flow distributor 550 may identify the first core 661 based oninformation (e.g., TCP tuple) included in the request 671. For example,an in one embodiment, the flow distributor 550 calculates a hash valuefor the first request 671 based on information (e.g., TCP tuple)included in the request 671. The flow distributor may identify the firstcore 661 from the calculated hash value. The flow distributor 550 maydetermine that the first core 661 is active and/or available to handlethe request 671. The flow distributor 550 may then forward the request671 to the first core 661. The first core 661 can receive the request671 via a transceiver 621 of the first core 661.

In further details of step 703, the first core establishes a sessionidentifier for the SSL session. Responsive to receiving the request 671,the first core may parse, extract or otherwise process information fromthe request 671. The first core 661 may parse the request 671 for asession identifier, if available. In some embodiments, an absence of asession identifier in the request 671 indicates that the request 671 isa request for establishing a new SSL session. The first core 661 mayperform authentication and/or authorization in connection with request671, for example, by applying at least one policy 657.

In some embodiments, the server 106 generates the session identifier668′ for the SSL session 641. The first core 661 may obtain the sessionidentifier 668′ from the server 106. In other embodiments, the firstcore 661 may generate the session identifier 668′ for the SSL session641. The session identifier 668′ may be generated via any program code,formulas or algorithms. In one embodiment, the server 106 and/or thefirst core 661 may generate a 16 byte session identifier 688′. In oneembodiment, the server 106 and/or the first core 661 may generate a 32byte session identifier 688′. In some embodiments, the server 106 and/orthe first core 661 may reserve 4 byte of the session identifier 688′ fortimestamp information. The server 106 and/or the first core 661 maygenerate a random session identifier 688′. The server 106 and/or thefirst core 661 may generate a session identifier 688′ using a cipher 631and/or a random code generator. The server 106 and/or the first core 661may apply at least one policy 657 in generating the session identifier688′. During generation of the session identifier 688′, The server 106and/or the first core 661 may determine that the session identifier 688′is unique for the multi-core system. In some embodiments, the sessionidentifier 668′ is generated after the SSL session 641 is established.In other embodiments, the session identifier 668′ is generated while theSSL session 641 is established.

In some embodiments, a SSL server or vserver generates the sessionidentifier. In other embodiments, the client 102 generates the sessionidentifier 688′. In some other embodiments, the session identifier 668′may be generated by a cipher 631 and/or an encryption engine 234.

In further details of step 705, the first core encodes the first coreidentifier 656 in the session identifier 688′ to form a second sessionidentifier 688. In some embodiments, the first core 661 uses anencoder/decoder pair or a cipher 631 to encode the first core identifier656 in the session identifier 688′ to form a second session identifier688. The first core 661 may encode a byte of the session identifier 688′with the core identifier 656 to form the second session identifier 688.The first core 661 may encode the core identifier into a plurality ofbits of the session identifier 688′ to form the second sessionidentifier 688. The first core 661 may determine at a predeterminedfrequency a predetermined set of one or more bytes of the sessionidentifier 688′ to encode to form the second session identifier 688. Thefirst core 661 may determine a predetermined set of one or more bytes ofthe session identifier 688′ to encode to form the second sessionidentifier 688. The first core 661 may determine a predetermined set ofone or more bits of the session identifier 688′ to encode to form thesecond session identifier 688. The first core 661 may encode the coreidentifier 656 as a bit pattern in the session identifier 688. The firstcore 661 may set or unset a number of bits in the session identifier 688to encode the core identifier 656.

The first core 661 may encode, with a block cipher, the core identifier656 and a validity identifier with the session identifier 688′ to formthe second session identifier 688. The first core 661 may encode thecore identifier 656 and/or a validity identifier with the sessionidentifier 668′ using a DES or 3DES cipher. The first core 661 may use 7bytes of the session identifier 688′ to encode the validity identifier.The first core 661 may use 8 bytes of the session identifier 688′ toencode both the core identifier 656 and the validity identifier. Themulti-core system, intermediary 200, a SSL server or a SSL vserver maygenerate the validity identifier.

In some embodiments, the first core 661 uses an encoder/decoder pair ora cipher 631 to encode the first core identifier and/or a validityidentifier in the session identifier 688′ to form a second sessionidentifier 688. In some embodiments, the first core 661 executes programcodes to encode the first core identifier 656 and/or a validityidentifier in the session identifier 688′ to form a second sessionidentifier 688. The first core 661 may also perform mapping or applyhash functions on session identifier 688′ before or after encoding. Thesecond session identifier 688 may be a result of mapping, hash functionsand/or encoding applied on the session identifier 688′. The first core661 may randomly select a byte location in the session identifier toencode the core identifier. The first core 661 may randomly select bytelocations in the session identifier to encode the validity identifier.

In further details of step 707, the first core establishes the SSLsession 641 with the client using the second session identifier 688. Thefirst core 661 may establish an SSL session 641 with a client responsiveto the request 671. The first core 661 may establish an SSL session 641with a client 102 responsive to successful authentication and/orauthorization. The first core 661 may initiate handshaking operationswith the client 102 and/or server 106, to establish one or moreconnections between the client 102 and the server 106. The first core661 may negotiate a SSL version with the client 102 and/or the server106. Upon reaching agreement of a SSL version, the first core 661 mayestablish a session protocol stack for a SSL session 641. The first core661 may execute one or more drivers and/or agents in the protocol stackin establishing the protocol stack. The first core 661 may establish oneor more connections between the client 102, server 106 and layers of thesession protocol stack. In addition, the first core 661 may establish asession data structure for the SSL session 641.

The first core 611 may perform any of the steps of establishing the SSLsession 641 via functionality provided by one or more of: the cipher631, the encryption engine 234 and/or a SSL vserver executing on thefirst core 611 or on the multi-core system. In addition, the SSL session641 may be generated based on application of at least one policy 657.The first core 611 may allocate memory for establishing and/ormaintaining the SSL session 641. Further, the first core 611 mayestablish the session data structure for the SSL session 641. In someembodiment, the backend server 106 establishes the SSL session 641 onbehalf of the first core 661.

In further details of step 709, the first core stores the second sessionidentifier 688 in a session cache 651 of the first core 661. The firstcore 661 may create or allocate memory for a session cache 651responsive to the request 671. The first core 661 may create or allocatememory for a session cache 651 responsive to successful authenticationand/or authorization.

The first core 661 may create a session cache 651 for one or more SSLsessions associated with the first core 661. The first core 661 maycreate a session cache 651 in association with establishing a SSLsession. In one embodiment, the first core 661 stores the secondidentifier 688 at a location in memory 667. The first core 661 may storethe second identifier 688 in a private memory space of the first core661. In one embodiment, the first core 661 stores the second identifier688 at a location in shared memory 667 accessible by a plurality ofcores.

In further details of step 711, the first core indicates whether the SSLsession is resumable. In one embodiment, the first core 661 of amulti-core system indicates that an SSL session 641 established by thefirst core 661 is resumable or non-resumable. In another embodiment, thefirst core 661 of the multi-core system deployed as an intermediary 200between the client 102 and a server 106 receives a notification that theSSL session 641 is resumable or non-resumable. The multi-core system orthe flow distributor 550 may determine that the SSL session 641 isresumable or non-resumable. The SSL session 641 may be resumable ornon-resumable based on a setting, preference or configuration associatedwith the client 102, the server 106 and/or the request 671. In stillanother embodiment, the first core 661 of the multi-core system deployedas an intermediary 200 between the client 102 and a server 106determines that the SSL session 641 is resumable or non-resumable inaccordance with a policy 656.

In some embodiments, the first core 661 identifies, via core identifiersincluded in requests for session information for the SSL session 641,one or more cores of the multi-core system that sent the requests. Thefirst core 661 may receive these requests as CCM messages from othercores. The first core 661 may receive these requests from other coresresponsive to a session disruption. The first core 661 may parse eachrequest for a core identifier, each core identifier identifying a corethat sent the request. The first core 661 can identify one or more coresbased on a bit pattern of data stored on the first core 661. The firstcore 661 can identify one or more cores based on a bit pattern of datastored in the memory 667. The first core 661 can identify the one ormore cores by comparing the core identifiers included in the requestswith the bit pattern.

In some embodiments, the first core 661 transmits to each of theidentified one or more cores of the multi-core system a messageindicating that the SSL session 641 is resumable or non-resumable. Thefirst core 661 may broadcast a message to each of the identified one ormore cores indicating that the SSL session 641 is resumable ornon-resumable. In some embodiments, the first core 661 sends a messageto each of the identified one or more cores if a resumable indicator 668is not available and/or not set.

In further details of step 713, the first core 661 sets an indicator 668at a location in memory 667 accessible by each core of the multi-coresystem. The indicator 668 indicates whether the SSL session 641 isresumable. In one embodiment, responsive to the indication, the firstcore 661 sets an indicator 668 at a location in memory 667 accessible byeach core of the multi-core system. The indicator 668 may indicate thatthe SSL session 641 is resumable or non-resumable. The indicator 668 maybe referred to as a resumable indicator 668. The first core 661 maystore, to the location in the memory 667, a value for a resumable fieldassociated with the SSL session 641 as the indicator.

In further details of step 715, a flow distributor 550 of the multi-coresystem forwards a second request 672 from the client 102 to a secondcore 662 to reuse and resume the SSL session 641. In some embodiments, aflow distributor 550 (e.g., receive side scaler) of the multi-coresystem determines to forward the request 672 to the second core 662based on a source port indicated by the request 672. The flowdistributor 550 may receive the second request 672 from the client 102.The flow distributor 550 may receive the second request 672 after adisruption related to the SSL session 641. The flow distributor 550 maydetermine to forward the request 672 to the second core 662 based anon-availability of the first core 661. The flow distributor 550 maydetermine to forward the request 672 to the second core 662 based on aTCP tuple indicated by the request 672. The flow distributor 550 maydetermine to forward the request 672 to the second core 662 based on ahash index determined from a TCP tuple indicated by the request 672. Theflow distributor 550 may determine to forward the request 672 to thesecond core 662 by associating the hash index with the second core 662.

In further details of step 717, the second core 662 receives the secondrequest 672 from the client 102. The request comprises the secondsession identifier 688. In some embodiments, the second core 662 of themulti-core system deployed as an intermediary 200 between the client 102and a server 106 receives the request 672 from the client 102 to resumethe SSL session 641 with the server. The second core 662 is assigned asecond core identifier 658. The multi-core system may assign the secondcore identifier 658 to the second core 662 based on an identifier of aprocessing unit of the second core 662. The multi-core system may assignthe core a one-byte core identifier 658. The multi-core system maygenerate for the second core identifier 658 a random and/or unique coreidentifier in the multi-core system.

The second core 662 can receive, via a transceiver 622 of the secondcore 662, the second request 672. The second core 662 may receive thesecond request 672 from the flow distributor 550. The second core 662may receive the second request 672 as a client-hello message. The secondcore 662 may receive the request 672 from a client 102 via a SSLsession. For example, a connection between the client and theintermediary 200 may be maintained but a connection between theintermediary 200 and the server 106 may be disrupted. The second core662 may receive the request 672 to resume and/or reuse the SSL session641.

The second request 672 may comprise a session identifier 688. The secondcore 662 may parse, extract and/or decode a session identifier 688 fromthe second request 672. The second core 662 may parse, extract and/ordecode this second session identifier 668 from the second request 672responsive to receiving the second request 672. The second core 662 maydecode the second session identifier 688 to extract a core identifier656 and/or validity identifier from the session identifier 688. Thesecond core 662 may apply mapping and/or hash functions on the sessionidentifier 688 before or after the decoding.

In some embodiments, the decoding process includes applying mappingand/or hash functions on the session identifier 688. Application ofmapping and/or hash functions may yield the original session identifiergenerated by the server 106 for the SSL session 641. The second core 662may apply this original session identifier in communications with theserver 106. The second core 662 may use this original session identifierto identify the server 106 and/or SSL session 641. In some embodiments,the second core 662 may check the session cache 652 against thisoriginal session identifier.

The second session identifier 688 may identify the first core 661 as anestablisher or owner of the SSL session 641. The second core 662, mayestablish that the validity identifier is valid by accessing relatedinformation from memory 667, applying at least one policy 656, and/orcommunicating with at least one of: the first core 661, the flowdistributor 550 and some other component of the intermediary 200.

In further details of step 719, and in one embodiment, the second core662 determines that the second session identifier 688 is not in asession cache 652 of the second core 662. In another embodiment, thesecond core 662 determines that the second session identifier 688 is ina session cache 652 of the second core 662. Responsive to obtaining thesecond session identifier 688, the second core 662 may access at leastone session cache 652 of the second core 662. The second core 662 mayretrieve the at least one session cache 652 from memory 667. The secondcore 662 may retrieve information from the session cache 652, such as asession identifier, to compare against the second session identifier688. Responsive to the comparison, the second core 662 can determinewhether the second session identifier 688 is in a session cache 652 ofthe second core 662. In some embodiments, if the second sessionidentifier 688 is in the session cache 652, the corresponding session isalready associated with the second core 662. Consequently, the secondcore 622 can resume the session and resume client communications withthe server 106 if other factors for resuming the session are met.

In further details of step 721, the second core decodes a coreidentifier 656 encoded in the second session identifier 688. The secondcore 662 may decode a second core identifier 656 from a byte of thesecond session identifier 688. The second core 662 may decode apredetermined byte of the second session identifier 688 to obtain thesecond core identifier 656. The second core 662 may apply a decoder todecode the second core identifier 656 to obtain the second sessionidentifier 656. The second core 662 may apply a cipher 632 (e.g., ablock cipher) to decode the second core identifier 656 to obtain thesecond session identifier 656. In other embodiments, the second core 662may use a DES or a 3DES cipher. The second core 662 may decode thesecond core identifier 656 from a predetermined number of bits in thesecond session identifier 688.

In further details of step 723, the second core 662 determines whetherthe indicator 668 in the memory location indicates that the SSL sessionis resumable. The second core 662 processing a request 672 to reuseand/or resume a SSL session 641 may access the resumable indicator 668to determine whether the SSL session 641 is resumable. The second core662 may access the resumable indicator 668 from memory 667. The secondcore 662 may access a copy of the resumable indicator 668, for example,from the private memory space of the second core 662. The second core662 may process the resumable indicator field or pointer destination todetermine whether the SSL session 641 is resumable. In one embodiment,the second core 662 may determine that a resumable indicator 668 of theSSL session 641 does not exist or is not set. In some embodiments, thesecond core 622 receives a notification or message from the first core661 or other component of the multi-core system on whether the SSLsession 641 is resumable.

In one embodiment, the resumable indicator 668 and/or notificationindicates that the SSL session 641 is non-resumable. In this embodiment,the second core 662 may determine not to resume the SSL session. Furtherdetails are described in connection with step 741. In anotherembodiment, the resumable indicator 668 and/or notification indicatesthat the SSL session 641 is resumable. In this embodiment, the secondcore 622 can resume the session and resume client communications withthe server 106 if other requirements for resuming the session are met(see step 729).

In further details of step 725, the second core determines whether areuse limit 678 for the SSL session has been exceeded. The second core662 may access the memory 667 (e.g., shared memory space or privatememory space) for a reuse limit 678. The second core 662 may set a reuselimit 678 for the SSL session 641, for example if a reuse limit 678 doesnot already exist. The second core 662 may compare the reuse limit 678against a reuse history, counter or tracker. The second core 662 mayaccess the memory 667 for the reuse history, counter or tracker.

In one embodiment, the second core 662 determines that the reuse limit678 for the SSL session has been exceeded. In this embodiment, thesecond core 662 may determine not to resume the SSL session. Furtherdetails are described in connection with step 741. In anotherembodiment, the second core 662 determines that the reuse limit 678 forthe SSL session has not been exceeded. Consequently, the second core 622can resume the session and resume client communications with the server106 if other requirements for resuming the session are met (see step729).

In further details of step 727, the second core 662 determines whetherthe core identifier 656 corresponds to the second core identifier 658.In one embodiment, the second core 662 identifies from encoding of thesecond session identifier 688 that the second core 662 is not theestablisher of the SSL session 641. For example, the second core 662 maydetermine that the core identifier 658 does not correspond to the secondcore identifier 656. In another embodiment, the second core 662 mayidentify from encoding of the second session identifier 688 that thefirst core 662 is the establisher of the SSL session 641. The secondcore 662 may send a message to the first core 661 to verify that thefirst core 662 is the establisher of the SSL session 641.

In still another embodiment, the second core 662 identifies fromencoding of the second session identifier 688 that the second core 662is the establisher of the SSL session. For example, the second core 662may determine that the core identifier in the received sessionidentifier matches the second core identifier 656. In this embodiment,the second core 622 can resume the session and resume clientcommunications with the server 106 if other requirements for resumingthe session are met (see step 729).

In further details of step 729, the second core 662 resumes clientcommunications with the server 106 in the SSL session. If the coreidentifier 658 of the second core 662 corresponds to the second coreidentifier 656, the second core 662 may resume client communicationswith the server in the SSL session 641 if other requirements forresuming the session is met. If the second core 662 determines that thesecond core 662 is the establisher of the SSL session 641, the secondcore 662 may resume client communications with the server in the SSLsession 641 if other requirements for resuming the session is met. Indifferent embodiments, some or all of the following requirements must bemet before the second core 662 can resume the SSL session 641:

i) the resumable indicator 668 (or a notification) indicates that thesession is resumable;

ii) the reuse limit 678 is not exceeded;

iii) the session is not expired; and

iv) the session is not corrupted.

In connection with resuming the session 741, the second core 662 mayupdate one or more of the: resumable indicator 668, the reuse limit 678and the associated session cache. The second core 662 may restart aportion of the session protocol stack and/or restore a connection of theSSL session 641 (e.g., a disrupted connection between the server 106 andthe protocol stack). In addition, the second core 662 may send a messageto the client 102. In some embodiments, the second core 662 may initiatehandshaking with the client to resume the SSL session 741, and mayinclude authentication and/or authorization process steps.

In further details of step 731, the second core 662 forwards the request672 to the server 106. The second core 662 may resume communicationswith the server 106 responsive to resumption of the SSL session 641. Inone embodiment, the second core 662 resumes client communications withthe server 106 from the point of disruption of the SSL session 641. Insome embodiments, the resumption of client communications is transparentor substantially transparent to one or more of: the user of the client,the client 102 and the server 106

In further details of step 733, the second core transmits a messagerequesting information about the SSL session 741 to the first coreidentified by the core identifier 656. The second core 662 may transmitto the core identified by the core identifier a message requestinginformation about the established SSL session 641. In some embodiments,the second core 662 determines that the second core 662 is not theestablisher of the SSL session 641. Responsive to the determination, thesecond core 662 may transmit a request to the core 661 that establishedthe SSL session 641. The second core 662 may transmit a request toverify that the first core is the establisher of the SSL session 641.

The second core 662 may transmit a request for information to reuse andclone the SSL session 641. The second core 662 may transmit a requestfor a minimum set of information to reuse and clone the SSL session 641on the second core 662. The second core 662 may transmit a request forat least a partial copy of the session data structure of the SSL session641. The second core 662 may transmit a request for at least a masterkey, a client certificate, a name of a cipher, a result of clientauthentication, and an SSL version to reuse and clone the SSL session641. The second core 662 may transmit a request for a key processingargument, a CRL and/or TCP tuple information. The second core 662 maytransmit the request or message as a CCM message.

In further details of step 735, the first core 661 identifies the secondcore 662 via a core identifier 658 included in the message received fromthe second core 662. In some embodiments, the first core 661 receivesthe message or request from the second core 662. The first core 661 mayparse or extract a core identifier 658 from the message or request toidentify the second core 662. Based on the identification, the firstcore 661 may respond to the second core 662.

In further details of step 737, the first core 661 transmits a messageto the second core 662. The first core 661 may transmit a message to thesecond core 662 responsive to the request or message from the secondcore 662. The first core 661 may send a confirmation message to thesecond core 662 that the first core 661 is the establisher of the SSLsession 641. Steps 739 and 743 describes other embodiments of the firstcore's responses.

In further details of step 739, the first core 661 transmits to thesecond core 662 the message indicating that the SSL session is notreusable or resumable. In some embodiments, this message is a CCMmessage. The first core 661 may transmit the message indicating that theSSL session is non-resumable based on the resumable indicator 668. Thefirst core 661 may transmit the message indicating that the SSL sessionis non-resumable based on a notification that the first core 661 havereceived. The first core 661 may transmit the message indicating thatthe SSL session is not reusable based on a reuse limit 678 of the SSLsession 641. The first core 661 may transmit the message indicating thatthe SSL session is not reusable or resumable based on an expiration ofthe SSL session 641. The first core 661 may transmit the messageindicating that the SSL session is not reusable or resumable based on adetermination that the SSL session 641 is corrupted. The first core 661may transmit the message indicating that the SSL session is not reusableor resumable based on detecting an error message in the SSL session 641.

In further details of step 741, the second core determines not to resumethe SSL session based on at least one of: the message from the firstcore, the identification that the second core is not the establisher ofthe SSL session, application of a policy, the indicator, and the reuselimit. The second core 662 may receive a message from the first core 661indicating that the SSL session 641 is not reusable or resumable basedon any of the reasons described in connection with step 739. The secondcore 662 may determine not to resume the SSL session 641 based on themessage from the first core 661. The second core 662 may determine notto resume the SSL session 641 based on limited resources available onthe second core 662.

The second core 662 may determine not to resume the SSL session 641based on a determination that the second core 662 did not establish theSSL session 641. The second core 662 may determine whether apredetermined maximum reuse threshold (e.g., reuse limit 678) has beenreached. The second core 662 may determine not to resume the SSL session641 if the maximum reuse threshold is reached or exceeded. The secondcore 662 may determine not to resume the SSL session 641 in the absenceof a reuse limit 678. The second core 662 may determine not to resumethe SSL session 641 based on a determination that the SSL session 641 isnon-resumable according to the resumable indicator 668.

In some embodiments, the second core 662 removes information about theSSL session 641 from a session cache 652 of the second core 662. Thesecond core 662 may remove a session cache 652 of the second core 662.The second core 662 may remove the information and/or the session cache652 responsive to a determination not to resume or reuse the SSL session641. In some embodiments, the second core 662 establishes a new SSLsession responsive to the client request 672. The second core maynegotiate with the client 102 for a new SSL version and/or send a newsession identifier to the client 102. Embodiments of details forestablishing a new SSL session is described above in connection step701.

In further details of step 743, the first core transmits, to the secondcore, at least one of: a master key, a client certificate, a name of acipher, a result of client authentication, and an SSL version in themessage. In one embodiment, the first core 661 transmits to the secondcore 662 a master key, a client certificate, a name of a cipher, aresult of client authentication, and an SSL version. The first core 661may also transmit information associated with key processing arguments,CRLs and TCP tuples. The first core 661 may send the second core 662 atleast a portion of the session data structure of the SSL session 641.

The first core 661 may send the second core 662 any other informationfor resuming or reusing the SSL session 641. The first core 661 may sendthe second core 662 a minimum set of information for resuming or reusingthe SSL session 641 in the second core 662. The first core 661 may sendthe second core 662 information for cloning or creating a copy of theSSL session 641 in the second core 662. The first core 661 may send anyof these information to the second core 662 in one or more messages. Theone or more messages may be sent via CCM. In some embodiments, the firstcore 661 may provide any of these information at a location in memory667 for the second core 667 to access. The first core 661 may alsoprovide the second core 662 a pointer or location to any of theseinformation.

In further details of step 745, the second core establishes a copy ofthe SSL session 641′ on the second core based on the information aboutthe SSL session obtained from the first core. In some embodiment, thesecond core 662 establishes a clone or copy of the SSL session 641′using one or more steps substantially similar to establishing a new SSLsession. The second core 662 may build a session data structure for theSSL session 641′ from a partial data structure of the original SSLsession 641 provided by the first core 661. The second core 662 mayinitiate handshaking steps with the client 102 and/or server 106. Thehandshaking steps may include any extent and combination ofauthentication, authorization, certificate validation/renewal, and keyvalidation/renewal depending on the information provided by the firstcore 661.

The second core 662 may generate a session identifier 688′ for thecloned SSL session 641′. The second core 662 may generate a sessionidentifier 688′ that is the same as the session identifier 688 for SSLsession 641 except for the encoded bits for the core identifier. Thesecond core 662 may encode the core identifier 658 of the second core662 in the session identifier 688′. A validity identifier for the SSLsession 641′ may be issued and encoded in the session identifier 688′.The second core 662 may create a session cache 652 in connection withestablishing the cloned SSL session 641′. The second core 662 may updatethe session cache 652 with the session identifier 688′. The second core662 may create and/or update the session cache according to embodimentsof steps described above in connection with FIG. 6 and steps 701 and707.

The second core 662 may update the resumable indicator 668, reuse limit678 and/or reuse count. The second core 662 may also send a message tothe first core 661 indicating that the cloned session 641′ is resumed.The first core 661 may update a record for tracking session reuse of theSSL session 641 amongst the plurality of cores. The first core 661 maymaintain the original SSL session 641 if any corresponding clonedsessions 641′ are active.

In further details of step 747, the second core 662 resumes clientcommunications with the server 106 with the copy of the SSL session641′. The second core 662 may resume client communications with theserver 106 with the cloned SSL session 641′ substantially similar to thesteps described in connection with steps 729 and 731. The second core662 may transmit a message to the client 102 and/or server 106 includingthe new session identifier 688′ and core identifier 658. In oneembodiment, the second core 662 resumes client communications with theserver 106 from the point of disruption of the original SSL session 641.In some embodiments, the resumption of client communications istransparent or substantially transparent to one or more of: the user ofthe client, the client 102 and the server 106.

Although generally discussed with respect to a first and a second core,the techniques in this disclosure can apply to any cores of themulti-core system. Various embodiments of the methods may include anycombination of the steps described. The systems and methods disclosedcan apply to homogeneous and heterogeneous system. Homogeneous systemsincludes but are not limited to i) cores in a multi-core system, ii) aplurality of multi-core systems, and iii) servers in a server farm.Heterogeneous systems includes but are not limited to i) general purposeCPUs and application specific cores, ii) a network of machines ofvarious types, iii) multi-core systems of different types and/or numberof cores, and iv) server farms comprising machines of different typesand/or number of machines.

In some embodiments, the systems and methods disclosed can be applied tocluster deployment where session cloning is performed across homogenousor heterogeneous systems. In one embodiment, a plurality of sessions ina first multi-core system may be cloned in a second multi-core system.In other embodiments, session information and parameters may be reusedacross homogenous or heterogeneous systems. In some embodiments, SSLsecurity parameters may be transferred across homogenous orheterogeneous systems. Some or all of a set of SSL security parametersmay be copied, regenerated, or otherwise reused in one or more cores ormachines. Examples of SSL security parameters include identification ofa secure port for SSL connection, the level or strength of encryption,the interval for session renegotiation, enablement of host matching andlocation of private key. Furthermore, reuse may include, but are notlimited to, information and/or parameters related to keys, encryption,certificates, ciphers, authentication results and SSL version.Embodiments of these information and/or parameters are described abovein connection with FIG. 6.

The systems and methods disclosed can also be applied to state-full SSLsession failover in homogenous or heterogeneous systems. In someembodiments, Active-Standby deployment may be available where a SSLsession established on an active node is cloned on a standby node. Whenfailover happens, the standby node can take over as the active node. TheSSL clients may not need to re-negotiate the SSL session as the newActive node already have the complete cloned session. The systems andmethods disclosed can be further applied to external heterogeneoussystems, such as those with well-defined authentication processes inplace to identify the external device performing session cloning.

G. Systems and Methods for Providing a Distributed Cluster Architecture

As discussed earlier, to overcome limitations on transistor spacing andCPU speed increases, many CPU manufacturers have incorporated multi-coreCPUs to improve performance beyond that capable of even a single, higherspeed CPU. Similar or further performance gains may be made by operatinga plurality of appliances, either single or multi-core, together as adistributed or clustered appliance. Individual computing devices orappliances may be referred to as nodes of the cluster. A centralizedmanagement system may perform load balancing, distribution,configuration, or other tasks to allow the nodes to operate inconjunction as a single computing system. Externally or to otherdevices, including servers and clients, in many embodiments, the clustermay be viewed as a single virtual appliance or computing device, albeitone with performance exceeding that of a typical individual appliance.

Referring now to FIG. 8, illustrated is an embodiment of a computingdevice cluster or appliance cluster 600. A plurality of appliances 200a-200 n or other computing devices, sometimes referred to as nodes, suchas desktop computers, servers, rackmount servers, blade servers, or anyother type and form of computing device may be joined into a singleappliance cluster 600. Although referred to as an appliance cluster, inmany embodiments, the cluster may operate as an application server,network storage server, backup service, or any other type of computingdevice without limitation. In many embodiments, the appliance cluster600 may be used to perform many of the functions of appliances 200, WANoptimization devices, network acceleration devices, or other devicesdiscussed above.

In some embodiments, the appliance cluster 600 may comprise a homogenousset of computing devices, such as identical appliances, blade serverswithin one or more chassis, desktop or rackmount computing devices, orother devices. In other embodiments, the appliance cluster 600 maycomprise a heterogeneous or mixed set of devices, including differentmodels of appliances, mixed appliances and servers, or any other set ofcomputing devices. This may allow for an appliance cluster 600 to beexpanded or upgraded over time with new models or devices, for example.

In some embodiments, each computing device or appliance 200 of anappliance cluster 600 may comprise a multi-core appliance, as discussedabove. In many such embodiments, the core management and flowdistribution methods discussed above may be utilized by each individualappliance, in addition to the node management and distribution methodsdiscussed herein. This may be thought of as a two-tier distributedsystem, with one appliance comprising and distributing data to multiplenodes, and each node comprising and distributing data for processing tomultiple cores. Accordingly, in such embodiments, the node distributionsystem need not manage flow distribution to individual cores, as thatmay be taken care of by a master or control core as discussed above.

In many embodiments, an appliance cluster 600 may be physically grouped,such as a plurality of blade servers in a chassis or plurality ofrackmount devices in a single rack, but in other embodiments, theappliance cluster 600 may be distributed in a plurality of chassis,plurality of racks, plurality of rooms in a data center, plurality ofdata centers, or any other physical arrangement. Accordingly, theappliance cluster 600 may be considered a virtual appliance, grouped viacommon configuration, management, and purpose, rather than a physicalgroup.

In some embodiments, an appliance cluster 600 may be connected to one ormore networks 104, 104′. For example, referring briefly back to FIG. 1A,in some embodiments, an appliance 200 may be deployed between a network104 joined to one or more clients 102, and a network 104′ joined to oneor more servers 106. An appliance cluster 600 may be similarly deployedto operate as a single appliance. In many embodiments, this may notrequire any network topology changes external to appliance cluster 600,allowing for ease of installation and scalability from a singleappliance scenario. In other embodiments, an appliance cluster 600 maybe similarly deployed as shown in FIGS. 1B-1D or discussed above. Instill other embodiments, an appliance cluster may comprise a pluralityof virtual machines or processes executed by one or more servers. Forexample, in one such embodiment, a server farm may execute a pluralityof virtual machines, each virtual machine configured as an appliance200, and a plurality of the virtual machines acting in concert as anappliance cluster 600. In yet still other embodiments, an appliancecluster 600 may comprise a mix of appliances 200 or virtual machinesconfigured as appliances 200. In some embodiments, appliance cluster 600may be geographically distributed, with the plurality of appliances 200not co-located. For example, referring back to FIG. 8, in one suchembodiment, a first appliance 200 a may be located at a first site, suchas a data center and a second appliance 200 b may be located at a secondsite, such as a central office or corporate headquarters. In a furtherembodiment, such geographically remote appliances may be joined by adedicated network, such as a T1 or T3 point-to-point connection; a VPN;or any other type and form of network. Accordingly, although there maybe additional communications latency compared to co-located appliances200 a-200 b, there may be advantages in reliability in case of sitepower failures or communications outages, scalability, or otherbenefits. In some embodiments, latency issues may be reduced throughgeographic or network-based distribution of data flows. For example,although configured as an appliance cluster 600, communications fromclients and servers at the corporate headquarters may be directed to theappliance 200 b deployed at the site, load balancing may be weighted bylocation, or similar steps can be taken to mitigate any latency.

Still referring to FIG. 8, an appliance cluster 600 may be connected toa network via a client data plane 602. In some embodiments, client dataplane 602 may comprise a communication network, such as a network 104,carrying data between clients and appliance cluster 600. In someembodiments, client data plane 602 may comprise a switch, hub, router,or other network devices bridging an external network 104 and theplurality of appliances 200 a-200 n of the appliance cluster 600. Forexample, in one such embodiment, a router may be connected to anexternal network 104, and connected to a network interface of eachappliance 200 a-200 n. In some embodiments, this router or switch may bereferred to as an interface manager, and may further be configured todistribute traffic evenly across the nodes in the application cluster600. Thus, in many embodiments, the interface master may comprise a flowdistributor external to appliance cluster 600. In other embodiments, theinterface master may comprise one of appliances 200 a-200 n. Forexample, a first appliance 200 a may serve as the interface master,receiving incoming traffic for the appliance cluster 600 anddistributing the traffic across each of appliances 200 b-200 n. In someembodiments, return traffic may similarly flow from each of appliances200 b-200 n via the first appliance 200 a serving as the interfacemaster. In other embodiments, return traffic from each of appliances 200b-200 n may be transmitted directly to a network 104, 104′, or via anexternal router, switch, or other device. In some embodiments,appliances 200 of the appliance cluster not serving as an interfacemaster may be referred to as interface slaves.

The interface master may perform load balancing or traffic flowdistribution in any of a variety of ways. For example, in someembodiments, the interface master may comprise a router performingequal-cost multi-path (ECMP) routing with next hops configured withappliances or nodes of the cluster. The interface master may use anopen-shortest path first (OSPF) In some embodiments, the interfacemaster may use a stateless hash-based mechanism for trafficdistribution, such as hashes based on IP address or other packetinformation tuples, as discussed above. Hash keys and/or salt may beselected for even distribution across the nodes. In other embodiments,the interface master may perform flow distribution via link aggregation(LAG) protocols, or any other type and form of flow distribution, loadbalancing, and routing.

In some embodiments, the appliance cluster 600 may be connected to anetwork via a server data plane 604. Similar to client data plane 602,server data plane 604 may comprise a communication network, such as anetwork 104′, carrying data between servers and appliance cluster 600.In some embodiments, server data plane 604 may comprise a switch, hub,router, or other network devices bridging an external network 104′ andthe plurality of appliances 200 a-200 n of the appliance cluster 600.For example, in one such embodiment, a router may be connected to anexternal network 104′, and connected to a network interface of eachappliance 200 a-200 n. In many embodiments, each appliance 200 a-200 nmay comprise multiple network interfaces, with a first network interfaceconnected to client data plane 602 and a second network interfaceconnected to server data plane 604. This may provide additional securityand prevent direct interface of client and server networks by havingappliance cluster 600 server as an intermediary device. In otherembodiments, client data plane 602 and server data plane 604 may bemerged or combined. For example, appliance cluster 600 may be deployedas a non-intermediary node on a network with clients 102 and servers106. As discussed above, in many embodiments, an interface master may bedeployed on the server data plane 604, for routing and distributingcommunications from the servers and network 104′ to each appliance ofthe appliance cluster. In many embodiments, an interface master forclient data plane 602 and an interface master for server data plane 604may be similarly configured, performing ECMP or LAG protocols asdiscussed above.

In some embodiments, each appliance 200 a-200 n in appliance cluster 600may be connected via an internal communication network or back plane606. Back plane 606 may comprise a communication network for inter-nodeor inter-appliance control and configuration messages, and forinter-node forwarding of traffic. For example, in one embodiment inwhich a first appliance 200 a communicates with a client via network104, and a second appliance 200 b communicates with a server via network104′, communications between the client and server may flow from clientto first appliance, from first appliance to second appliance via backplane 606, and from second appliance to server, and vice versa. In otherembodiments, back plane 606 may carry configuration messages, such asinterface pause or reset commands; policy updates such as filtering orcompression policies; status messages such as buffer status, throughput,or error messages; or any other type and form of inter-nodecommunication. In some embodiments, RSS keys or hash keys may be sharedby all nodes in the cluster, and may be communicated via back plane 606.For example, a first node or master node may select an RSS key, such asat startup or boot, and may distribute this key for use by other nodes.In some embodiments, back plane 606 may comprise a network betweennetwork interfaces of each appliance 200, and may comprise a router,switch, or other network device (not illustrated). Thus, in someembodiments and as discussed above, a router for client data plane 602may be deployed between appliance cluster 600 and network 104, a routerfor server data plane 604 may be deployed between appliance cluster 600and network 104′, and a router for back plane 606 may be deployed aspart of appliance cluster 600. Each router may connect to a differentnetwork interface of each appliance 200. In other embodiments, one ormore planes 602-606 may be combined, or a router or switch may be splitinto multiple LANs or VLANs to connect to different interfaces ofappliances 200 a-200 n and serve multiple routing functionssimultaneously, to reduce complexity or eliminate extra devices from thesystem.

In some embodiments, a control plane (not illustrated) may communicateconfiguration and control traffic from an administrator or user to theappliance cluster 600. In some embodiments, the control plane may be afourth physical network, while in other embodiments, the control planemay comprise a VPN, tunnel, or communication via one of planes 602-606.Thus, the control plane may, in some embodiments, be considered avirtual communication plane. In other embodiments, an administrator mayprovide configuration and control through a separate interface, such asa serial communication interface such as RS-232; a USB communicationinterface; or any other type and form of communication. In someembodiments, an appliance 200 may comprise an interface foradministration, such as a front panel with buttons and a display; a webserver for configuration via network 104, 104′ or back plane 606; or anyother type and form of interface.

In some embodiments, as discussed above, appliance cluster 600 mayinclude internal flow distribution. For example, this may be done toallow nodes to join/leave transparently to external devices. To preventan external flow distributor from needing to be repeatedly reconfiguredon such changes, a node or appliance may act as an interface master ordistributor for steering network packets to the correct node within thecluster 600. For example, in some embodiments, when a node leaves thecluster (such as on failure, reset, or similar cases), an external ECMProuter may identify the change in nodes, and may rehash all flows toredistribute traffic. This may result in dropping and resetting allconnections. The same drop and reset may occur when the node rejoins. Insome embodiments, for reliability, two appliances or nodes withinappliance cluster 600 may receive communications from external routersvia connection mirroring.

In many embodiments, flow distribution among nodes of appliance cluster600 may use any of the methods discussed above for flow distributionamong cores of an appliance. For example, in one embodiment, a masterappliance, master node, or interface master, may compute a RSS hash,such as a Toeplitz hash on incoming traffic and consult a preferencelist or distribution table for the hash. In many embodiments, the flowdistributor may provide the hash to the recipient appliance whenforwarding the traffic. This may eliminate the need for the node torecompute the hash for flow distribution to a core. In many suchembodiments, the RSS key used for calculating hashes for distributionamong the appliances may comprise the same key as that used forcalculating hashes for distribution among the cores, which may bereferred to as a global RSS key, allowing for reuse of the calculatedhash. In some embodiments, the hash may be computed with input tuples oftransport layer headers including port numbers, internet layer headersincluding IP addresses; or any other packet header information. In someembodiments, packet body information may be utilized for the hash. Forexample, in one embodiment in which traffic of one protocol isencapsulated within traffic of another protocol, such as lossy UDPtraffic encapsulated via a lossless TCP header, the flow distributor maycalculate the hash based on the headers of the encapsulated protocol(e.g. UDP headers) rather than the encapsulating protocol (e.g. TCPheaders). Similarly, in some embodiments in which packets areencapsulated and encrypted or compressed, the flow distributor maycalculate the hash based on the headers of the payload packet afterdecryption or decompression. In still other embodiments, nodes may haveinternal IP addresses, such as for configuration or administrationpurposes. Traffic to these IP addresses need not be hashed anddistributed, but rather may be forwarded to the node owning thedestination address. For example, an appliance may have a web server orother server running for configuration or administration purposes at anIP address of 1.2.3.4, and, in some embodiments, may register thisaddress with the flow distributor as its internal IP address. In otherembodiments, the flow distributor may assign internal IP addresses toeach node within the appliance cluster 600. Traffic arriving fromexternal clients or servers, such as a workstation used by anadministrator, directed to the internal IP address of the appliance(1.2.3.4) may be forwarded directly, without requiring hashing.

G. Systems and Methods for SSL Session Management in a Cluster System

In some aspects, the present disclosure is directed towards methods andsystems for SSL session management in a cluster system. A device,appliance, network or intermediary between one or more client andservers, may include a cluster or group of nodes (hereafter sometimesgenerally referred to as an “intermediary”, “cluster” or “clustersystem”). Each of these nodes may comprise a multi-core system and mayhost one or more processing engines (PEs) for handling packets. Thepresent methods and systems can efficiently manage SSL sessionsestablished across nodes and/or cores, including nodes having symmetricor asymmetric configuration. By interoperating between nodes within thecluster system, the nodes can present a single node image to a user ordevice interfacing with the cluster system. These methods and systemscan use a distributed hash table (DHT), that may allow any corereceiving a session resume/reuse request, to identify an owner code ofthe requested session. The distributed hash table can receive as input akey derived from a session identifier, to output information about theowner core. Copies of the distributed hash table may be available toeach core and/or node, and can be used to mark particular sessions thatmay be invalid or non-resumable. Based on the has table, the receivingcore may request for session information related to the requestedsession. The receiving core may then establish a local cloned session ofthe requested session, responsive to the session resume/reuse request.

Referring now to FIG. 9A, one embodiment of a system for SSL sessionmanagement in a cluster system is depicted. In brief summary, the systemincludes an intermediary 200, comprising a cluster system, thatfacilitates and/or processes communications between a client 102 and aserver 106 over at least one communication session. The cluster maycomprise any embodiment of features described above in connection withFIG. 8. Each node of the cluster may include a plurality of cores orpacket processing engines (PEs), such as various embodiments of thecores or PEs described above in connection with sections B-G. Each coremay include a hash table, which may comprise a copy or a portion of adistributed hash table (DHT) maintained within the cluster.

In some embodiments, each node of the cluster may comprise one or morefunctionality of an appliance having multi-core features, such asembodiments of appliances 200 described above in connection with atleast FIGS. 5A-5C, 6 and 7A-7B. A pair of nodes may communicate orexchange messages between themselves using node-to-node (N2N) messages,as discussed in section G. Each core or PE of a node may establishand/or maintain a N2N channel or connection to each of the other nodes.The configuration of the nodes may not be symmetric. For example, somenodes may comprise a larger number of cores and/or have access todifferent resources, or may comprise cores of different performanceand/or features than those of certain other nodes.

In some aspects, SSL session management may require particular attentionor handling in a cluster-based system or architecture. A SSL sessiondata structure can hold information that can be used to allow resumptionor cloning of existing SSL sessions. A SSL session data structure can bebuilt or replicated using certain session data that may be stored in aDHT. In some embodiments of the present systems, SSL session resumptionor reuse may be commonly used, for example, in applications involvingsecure communication. SSL session resumption or reuse may be used toreduce processing or communications load on a web-server, e.g., byavoiding or reducing full handshake processing.

In certain embodiments of a cluster system, SSL sessions created orestablished on a particular core of a node may be private to, orreserved for that core. Other cores of the same node, as well as ofdifferent nodes, may not be able to have direct access to session dataand/or session states of such an SSL session. Certain embodiments of thesystem may employ or be subject to processes or features that direct ordistribute incoming packets or requests across nodes and/or cores of theintermediary. By way of illustration, and not intended to be limiting inany way, the system may comprise RSS features (e.g., as described abovein connection with at least FIG. 5B) and/or CITRIX data flow diagram(DFD) features. Such features may make it likely for, or result insession resume/reuse requests or connections going to a different core,e.g., (node, core) pair, than the one (owner core) which established orallocated the session. For example, RSS and/or DFD may distribute packetor message load across nodes and/or cores of the cluster system, and maydo so without regards to (e.g., without the ability to determine) theidentity of the corresponding owner nodes and/or cores.

In certain embodiments, the intermediary provides a mechanism toidentify the owner (node, core). The latter may sometimes be referred toas an owner node of a session, so that a core of the node may own orhandle the session at the core level. The owner (node, core) maysometimes be referred to as an owner core of a session, such that thecore (owning or handling the session at the core level) may belong to anode referred as an owner node (owning or handling the session at thenode level). More generally, a (node, core) may sometimes be referred toby the corresponding node or core, and it should be understood that areferenced node would have an associated core, and a referenced corewould have an associated node.

A (node, core) may receive a session resume/reuse/cloning request(hereafter sometimes generally referred to as a “request”). Such a(node, core) may hereafter sometimes generally be referred to as a“receiving core”. The request may include a session identifier for arequested session. The request may include a request to access aparticular session, e.g., established with a server, or to beestablished with the server. The request may include a request to accessfeatures and/or resources provided by or available through a session,but may not necessarily comprise a request to access the requestedsession itself. The request may include a request to clone, reuse and/orresume a session, e.g., resume a session that was established by anothernode and/or core, or to reuse a session established at the receivingcore. The cloning and/or resumption of a requested session on anon-owner node and/or core may involve having the cloned/reused/resumedsession incorporating or making available certain features and/orresources provided by or available through the requested session.

In some embodiments, the request includes a Client-Hello message, orother handshaking message or packet. The request may include a messagesent or conveyed from a client to the server and/or intermediary. Therequest may include a message for accessing and/or establishing asession or connection of any type or form (e.g., a SSL session) with theserver and/or intermediary. The request may include a sessionidentifier, which can include any type or form of information foridentifying a session and/or a type of session. The request may includea request for information that an owner (node, core) may provide to annon-owner (node, core), e.g., to replicate a session structureconsistent or compatible with a particular session or session identifier(hereafter sometimes referred to as “session-ID”).

By identifying the owner (node, core) for a given session-ID, thecluster system can apply its N2N message passing mechanism to receiveinformation, enabling a receiving core to make or establish a copy orclone of the session. The receiving core may establish the copy or clonelocally, e.g., in or from the receiving core. The receiving core mayestablish the copy or clone in or from a cache of the requesting core.

The intermediary may include a hash table mechanism for identifying anowner of a session. The intermediary may, in certain embodiments,include a distributed hash table (DHT). The intermediary may include ashared hash table, e.g., in shared memory, which may be shared oraccessible by nodes and/or cores. In some embodiments, a DHT comprises amechanism, data structure, infrastructure or system for storing and/orretrieving data regarding sessions (e.g., session identifier, ownershipinformation, and session status such as validity,resumability/reusability). Each core of a node may have its own DHTtable, or a copy of the DHT. Each data item in a DHT may be indexed byan unique key. The unique key may be specified (e.g., in form and/or invalue) by an application which uses the DHT. For example, in an SSLapplication, a packet engine (PE) establishing or accessing a sessionmay access or interface with a DHT using one or more predefined APIs,which may be provided by the DHT.

In some embodiments, a pair of <data, key> is called a DHT entity. DHTentities may be stored in a DHT table. The data may include anyinformation about a session, such as owner core identification and/orinformation for cloning a session. A DHT can identify, determine orcompute the identity of an owner of an entity (or session) based on thekey. By having local or distributed copies of the DHT at each (node,core), applications using DHT may not have to be aware of a location(e.g., shared location) for fetching and/or storing the data that can beaccessed. By way of example, various operations can be made on a DHT,including but not limited to the following embodiments:

Dht_put(key, data): Stores the data on (or in association with) theowner (node, core).

Dht_get(key,): Fetches the data from (or in association with) the owner(node, core).

Dht_entry_delete(dht_entry): Deletes the dht_entry associated with theapplication's structure.

Dht_update(Key, Oldvalue, Newvalue): Updates Oldvalue with Newvalue onall or some of the (node, core), e.g., where ever (Key, Oldvalue)exists.

In some embodiments, a receiving core (sometimes referred to as arequesting core) can form or generate a key based at least in part on asession-ID (e.g., received from the client in the request). Thereceiving core can form or generate a key based at least in part on aunique identifier value of a vserver, VIP, packet processing engine orPE on which the receiving core received the request. For example, thereceiving core may apply a predefined transformation or encodingfunction/scheme to any of the information to form a key.

In certain embodiments, the data portion of a DHT entity may include oneor more of (e.g., at least) the following information, though notlimited to these:

-   -   session->master_key[48]    -   Client certificate, (e.g., if client Authentication along with        SSL data insertion is enabled on the SSL vserver/service). Data        insertion related to client certificate may require copying of        the client certificate. This may be variable in size, and may        involve additional overheads.    -   Identification of a method or means to recreate the        session->cipher pointer. For example, this may include a name of        a cipher passed in the core-to-core (or N2N) message. This        information may comprise 32 bytes of data.    -   Session->verify_result: This may hold or specify a result of        client authentication, and may be used in policy-based client        authentication. This information may comprise 4 bytes of data.    -   Session->ssl_version: This may hold or specify a version of SSL        negotiated for the session. This information may comprise u16        bits of data.    -   Session->key_arg[8]: This may be used in SSLv2 protocol.

The following is a non-limiting illustration of one embodiment offormats and/or data structures for keys and data (e.g., that can be usedwith DHT APIs for SSL):

typedef struct ssl_sess_dht_key { u16bits version; u64bits uniq_id;u08bits session_id_length; u08bitssession_id[SSL_MAX_SSL_SESSION_ID_LENGTH]; }ssl_sess_dht_key_t;Data (e.g., transferred for session cloning):

typedef struct ssl_sess_dht_st { u32bits size; u32bits verify_result;u32bits cipher_id; u32bits peercertlen; u32bits d_flags; u08bitskey_arg[SSL_MAX_KEY_ARG_LENGTH]; /* 8 */ u8bitsmaster_key[SSL_MAX_MASTER_KEY_LENGTH]; /* 48 */ u16bits flags; u16bitsssl_version; u16bits sni_len; u16bits master_key_length; u08bitskey_arg_length; u08bits cert_index; }ssl_sess_dht_t;

In certain embodiments, session creation or resumption/reuse using a DHTwithin a cluster system may involve a number of steps that may bedifferent from that of a mere or typical multi-core system. Some or allof the following steps may be described with respect to a front-end side(e.g., between a client 102 and the intermediary). In general forexample, upon receiving a new SSL connection request (e.g., nativeClient-Hello, or Client-Hello with no session-ID), the cluster systemmay create and/or assign a new session-ID responsive to the request. Thecluster system may (e.g., call an operation, dht_puhkey, data) to)install the requested session on the owner (node, core), e.g., the corethat was assigned or received the request for the (new) session.

On receiving a session resume/reuse request (e.g., a Client-Hello withsession-ID), the cluster system or receiving core may perform one ormore of the following. If the requested session is present or identifiedon a local cache of the receiving core, the receiving core may proceedto reuse the session. The receiving core may increment the reuse count,e.g., to indicate the reuse/resumption of the session. If the requestedsession is not present or identified on a local cache of the receivingcore, the cluster system or receiving core may (e.g., call an operation,dht_get(KEY) to) determine if the requested session is present oravailable on the owner (node, core).

If the requested session is present or available on the owner (node,core) (e.g., if the dht_get response is positive), it may mean that theowner (node, core) still maintains the session, and the owner mayprovide (e.g., in the response) session information for performing aresumption of the session on the current (node, core). If the requestedsession is not present or available on the owner (node, core) (e.g., ifthe dht_get response is negative), the session may have expired on theowner (node, core). In this case, the current or receiving core canissue a new session-ID, may establish a session corresponding to thesession-ID, and may add the session-ID to the core's own cache. Thereceiving core may (e.g., invoke an operation, dht_put(KEY,DATA) to)install the session on the owner (node, core).

Each session structure may be associated with a DHT entry in a DHT. If asession is to be freed or to expire, the cluster system or owner coremay (e.g., use the DHT API to) delete the DHT entry, which may beupdated to copies of the DHT at each (node, core). In some embodiments,an owner session is a session which is installed by DHT using a dht_putoperation. Other sessions may be referred to as cached sessions orcloned sessions. As discussed above, the core that establishes orinstalls a session (e.g., calls the dht_put operation) may not be theowner of the session. Ownership of a session may be determined by a DHTbased on the particular key (e.g., formed by a receiving core).

In some embodiments, cached sessions are created or established inresponse to an action of an non-owner receiving core (e.g., via thedht_get(key) operation). A cached session may send heart beat signals,or any other type of indication, to the corresponding owner session orowner (node, core). This may ensure that the owner session is notdeleted when it has cloned references (sessions) at other nodes orcores. Thus, at any time for a given owner session, there may existmultiple cached sessions.

In some embodiments, on the backend side (e.g., between the intermediaryand the server 106), the intermediary (e.g., a Netscalar node) may bethe SSL client. A SSL web server or the server 106 may issue asession-ID or session identifier. Each core (e.g., of the clustersystem) may open a session to the backend server. There may be norequirement for session-cloning. Each core may try to reuse the sessionto a backend server (e.g., for a predetermined limit, such as a maximumof 100 times or instances).

In session resume, a cluster system may clone a SSL session acrosscores. On receiving a session reuse/resume request on a receiving core,the core may check for the session in the receiving core's local cache.If the session exists on the same core, the session may be reused. Ifnot, the session may be cloned (e.g., copied) from the owner (node,core) to the receiving or current (node, core). As discussed, DHT may beused to facilitate or perform the cloning, e.g., by invoking thedht_get(key) operation. Cloning may not mean that an entire SSL sessiondata structure has to be copied. The cluster system may need to copyonly required or minimal information from the session data structure tohonor the session resumption. For example, the owner (node, core) mayperform a DHT lookup using the key as formed and received from therequesting core. The owner core may generate and send a responsecomprising data (e.g., minimal data) to recreate a requested sessionstructure or features. In some embodiments, session cloning may fail ifthe requested session does not exist (e.g., has expired) on the owner(node, core).

In certain embodiments, each core may perform (e.g., its own) sessionageing, which may be irrespective of whether the corresponding sessionis local or copied from an owner core. The cluster system or owner coremay invoke a “session free” function when references (e.g., all SPCBreferences) to the session have ceased or become zero. When a “sessionfree” function is called, a call may be made to an operation (e.g., to aDHT API dht_entry_delete operation) to check whether a DHT pointerassociated with the session structure can be deleted. In oneillustrative, nonlimiting embodiment, this operation may perform thefollowing checks: check whether the session is an owner session and thecorresponding DHT entry has aged out or not. If not, the operation mayreturn a failure to the “session free” function. If the session is notan owner session, the corresponding DHT entry can be deletedautomatically, and the operation may return a success to the “sessionfree” function. If all cached sessions are deleted or freed, thecorresponding owner session may not receive any heart beat signals, andthe owner session may be deleted, for example, in a next function callto “session free”. An owner session may be deleted after all the cachedsessions are deleted.

In some cases (e.g., in some front-end cases), the cluster system maydetermine that a session is not resumable. For example, if any fatalalert is sent or received in connection with a SSL session, the sessionmay be marked (e.g., by the owner core or the cluster system, in theDHT) as not resumable. All further SSL session resume requestscorresponding to that session may be discarded or rejected. It may behelpful to recognize that in a single core system, there may be one copyof a session's session entry. Thus, as soon as the session is marked notresumable, the information may be available for all subsequent sessionresume requests, e.g., session->not_resumable=1. In a cluster system, onthe other hand, a session entry may be owned by one core (owner core).Other (node, core)'s may have copies or access to the entry, e.g.,depending on which core received the session resume request. If thesession is to be marked as not-resumable in a core (owner or non-owner),the information may be updated such that it is accessible to each corehaving a reference (e.g., copy) to the session. In some embodiments, thecluster system uses a DHT API to perform the update.

The cluster system may include a DHT API or operation, sometimesreferred to as dht_update. When a session has a status change (e.g., ismarked not resumable on a core), the core can send an dht_update(key,oldvalue, newvalue) operation to the owner (node, core). The owner(node, core) can send a broadcast message to nodes and/or cores (e.g.,to all cores, or to cores having a reference or cached session) toupdate the oldvalue (e.g., valid or resumable) to newvalue (e.g., notresumable, expired, or invalid). If, for any reason, the dht_updateoperation's message cannot be conveyed across, the cluster system canqueue the corresponding session in a list, and may retry or re-invokethe same operation until the operation succeeds.

In some embodiments, and in the case of backend SSL sessions forexample, each core may open a SSL session to the backend server. Sincesessions may not be shared between the cores, each core can maintain itssession status (e.g., not-resumable) for incoming requests. For example,each core can mark its own local session as not-resumable. Because thesessions are not shared across cores, each core can maintain its owncount of a maximum reuse limit of the session.

The cluster system may support re-handshake operations. In someembodiments, and in the front-end for example, a re-handshake (e.g., aSSL Re-handshake) may operate similarly on a core that owns a session ason a core having a reference copy. During re-handshake, a new sessionmay be created on the core on which re-handshake is taking place. Theold session can still exists as the old session is not markednot-resumable (or invalid or expired).

The cluster system may support SSL data insertion. SSL data insertioninvolving client certificates may require a client certificate to becopied, e.g., from the DHT or from the owner core, to a core which hasreference copy of the session. When session cloning is complete, aclient's certificate may be copied in addition to session data structurecontents. Other pointers holding the Intermediate-CA certificate chainsent by the client may not be copied in some embodiments. In some cases,such pointers may not be valid on the core which does not own thesession.

Referring now to FIG. 9B, one embodiment of a method for managing one ormore SSL sessions in a cluster system is depicted. The method mayinclude receiving, by a first node from a cluster of nodes intermediarybetween a client and a server, a first request from the client to use afirst session established with the server (901). The first request mayinclude a session identifier of the first session. The first node maydetermine that the first session is not identified in a cache of thefirst node (903). The first node may identify, via a hash tableresponsive to the determination, an owner node of the first session fromthe cluster of nodes using a key (905). The key may be determined basedon the session identifier. The first node may send a second request tothe identified owner node for session data of the first session (907).The session data may be for establishing a second session with theserver. If the response does not include the session data, the firstcore may establish a new session responsive to the session reuse request(909). If the response includes the session data, the first core mayestablish the second session cloned from the first session (911).

Referring to (901) and in further details, a first node (e.g., areceiving node) from a cluster of nodes intermediary between a clientand a server may receive a first request from the client to use a firstsession established with the server. The cluster may be intermediarybetween at least client and at least one server. In some embodiments, adistributor module or mechanism of the intermediary may direct therequest to the first node. The first/receiving node may receive arequest to reuse, resume, clone, access or otherwise use a sessionpreviously established with the server. The receiving node may receive arequest to use or access a SSL session, for example, between the clientand the cluster, which may be referred to as a front-end side session.The receiving node may receive a request to use or access a SSL sessionbetween the cluster and the server, which may be referred to as aback-end side session. The receiving node may receive a request to useor access a SSL session between the client and the server. A core of thefirst node may be identified by the first node to receive a sessionreuse/resume/clone request.

The client may have, or may not have knowledge about the requestedsession. The session may be active or inactive, valid or invalid,expired and/or unexpired, reusable or non-reusable, and/or resumable ornon-resumable. The session may have been transferred from one node orcore to another node or core, or is in the process of being transferred.The client may be trying to access or resume a previous session (e.g.,the requested session) with the server. The client may generate and sendthe request identifying the first session. The first request may includea session identifier of the first session. The session identifier may beused to identify the requested session. The first request may include aconnection identifier, and/or any other identifier associated with thefirst session, for example, an identifier of an application executing onthe client, an identification of a user, an identifier of URL of aresource of the server, an IP address and/or port number of the clientand/or server. The session identifier may comprise an identifiergenerated from any of these information, and may be assigned to thefirst session, the user, the client, the application, the resourceand/or the server.

The receiving node may intercept or receive the request from the client.If the request does not include a session identifier, the receiving nodemay create or assign a new session identifier. The receiving node may,for example, establish a session local to the corresponding receivingcore's cache, responsive to the request and/or session identifier. Insome embodiments, the client generates and/or sends the request as partof a handshaking process for reusing, resuming, cloning or otherwiseestablishing a SSL session with the cluster and/or server. The first orreceiving node may receive the request from the client as part of ahandshaking process, e.g., a SSL handshaking process. The first orreceiving node may receive the request for establishing a SSL sessionwith the cluster and/or server. For example, the first node may receivea client-hello message that includes a session identifier for therequested session. The receiving node, e.g., a first (node, core) of thecluster system may receive the request, e.g., as discussed above inconnection with FIG. 9A. The receiving node may receive the requestcomprising one or more packets. The request may be sent, directed orassigned to the receiving core by the cluster, another node of thecluster system, or a flow distributor mechanism or feature associatedwith the cluster system (e.g., RSS and/or DFD).

Referring to (903) and in further details, the first node may determinewhether the first session is identified or referenced in a cache of thefirst node. The first node may determine whether the first session isidentified or referenced in a cache of a core of the first node. Forexample, the first node may check a cache of some or all cores of thefirst node. The first node may determine whether a session description,data structure, configuration, log file and/or status of the firstsession is stored in the cache or other location. For example, areceiving core may search a log file of the first node for any match orreference to the session identifier. The receiving or first node maydetermine that the (e.g., first) session is not identified in a cache ofthe receiving node. The receiving node may determine if the session isidentified in a local cache of a corresponding receiving core. Thereceiving core may determine that the first session is not identified inthe cache based on the session identifier of the first session. Thereceiving core may determine this based on a search or match againstdata maintained in the cache, for example.

The receiving node may determine if any sessions (e.g., sessions thatmay be active, established, inactive, resumable, etc.) are associatedwith the receiving core or its cache. The receiving node may determineif any sessions are owned by a core of the receiving node. The receivingnode may compare or match the session identifier with those of sessionsassociated with the receiving node or its cache(s). The receiving nodemay determine that the session is not identified in cache(s) of thenode's core(s), based on an absence of any sessions associated with thereceiving node or the cache(s). The receiving node may determine thatthe session is not identified in cache(s) of the node's core(s), basedon a comparison of the session identifier with those of sessionsassociated with the receiving node or the cache(s).

The receiving/first node may determine that the first node is not theowner node of the first session, e.g., responsive to the determinationor comparison. The receiving/first node ma determine that the first nodeis not the owner node of the first session, based on the sessionidentifier. The receiving/first node ma determine that the first node isnot the owner node of the first session, based on an absence of anysession maintained, established and/or referenced in the first node'scache(s). The receiving/first node ma determine that the first node isnot the owner node of the first session, based on information maintainedin a hash table, for example a DHT as described above in connection withFIG. 9A

In some cases, the receiving node may determine that the session isidentified in a cache of the receiving core. The receiving node maydetermine that it is the owner node of the requested session. Thereceiving node may proceed to reuse or resume the session, e.g., if thesession is valid, reusable, resumable and/or unexpired. If the sessionis invalid, not reusable, not resumable or expired, a receiving core ofthe receiving node may re-establish the session, e.g., based on sessiondata recovered from or stored for the session. If the session isinvalid, not reusable, not resumable or expired, the receiving core mayestablish a session (e.g., a new session) responsive to the request.

Referring to (905) and in further details, the first node may identify,via a hash table responsive to the determination, an owner node of thefirst session from the cluster of nodes using a key. For example, a coreof the first node may generate the key based on at least one of thesession identifier or a unique identifier of an entity (e.g., the clientor an application) from which the first request is received. The key maybe determined based on the session identifier. The key may be determinedbased on the unique identifier, which may comprise an IP address, avirtual IP address, a network identifier and/or a port number. The keymay comprise a hash table key of a distributed or shared hash table. Thereceiving or first node may identify an owner node of the first sessionusing the key. If the receiving node determines that the session is notidentified in a cache of the receiving node, the receiving node mayaccess a hash table, for example a DHT as described above in connectionwith FIG. 9A.

The receiving node may receive and/or store a copy of the hash table.The receiving node may receive and/or store a portion of the hash table.The receiving node may send a query to the hash table, e.g., using thekey. The receiving node or core may access a hash table via an API,which may include or support one or more functions or operations (e.g.,dht_get, as discussed above in connection with FIG. 9A). A receivingcore of the receiving node may compute, calculate, determine, form orotherwise generate a key based on data comprising at least one or bothof the session identifier and a unique identifier of an entity from/atwhich the request is received (e.g., a VIP, PE, node). The receivingcore may form the key by applying a predefined function ortransformation on the data.

The receiving node may use the key to index into the hash table, whichmay be a copy or a portion (e.g., a local copy) of a distributed orshared hash table of the cluster system. For example, the receiving coremay use the API to invoke an operation (e.g., dht_get operation), toaccess the hash table. The hash table may output, return or provide anidentification of the owner core based on the key. The receiving coremay use the key to index into or otherwise access the hash table todetermine if the session is valid, resumable and/or available at theowner core.

Referring to (907) and in further details, the receiving/first core maysend a second request to the identified owner node for session data ofthe first session. The receiving/first core may send the second requestresponsive to identification of the owner core. The receiving/first coreor the cluster system may request a response (e.g., from the owner coreor from the hash table) for session data of the (e.g., first) session.In some embodiments, the receiving/first core may access the hash tablefor at least a portion of the session data, e.g., using the key.

The receiving/first core may send a second request to initiate, clone orotherwise establish a second session. For example, the receiving/firstcore may send a second request to initiate a handshake for establishingthe second session. The session data may be for establishing a secondsession with the server. The session data may be for creating a secondsession cloned from the first session. In some embodiments, thereceiving core may request the response via the API, e.g., as part ofthe dht_get operation or step. Responsive to the operation (e.g., usingthe key to index into or otherwise access the hash table), the hashtable or the owner core may return or provide a set of data. The set ofdata may include session data or data associated with the requestedsession. The session data may be used by the receiving core to establisha second session, e.g., by cloning or making a copy of the requestedsession.

The session data may be for creating a second session with certainaspects (e.g., data structure, settings, policies, configuration,communication protocol) similar to or the same as the first session. Forexample, the session data may include SSL configuration and/or otherinformation, such as authentication settings for the second session. Insome embodiments, the first node may request for session data includinga status of the first sessions, e.g., whether the first session can bereused, resumed and/or cloned. For example, the first node may requestfor session data including a reuse or resume limit for the firstsession. The first node may receive a response to the second request,the response indicating that the requested first session is invalid,expired and/or not resumable. The first node may receive a response tothe second request, the response indicating that the requested firstsession is valid, unexpired and/or resumable.

Referring to (909) and in further details, if the response does notinclude the session data, the receiving/first core may establish a newsession responsive to the session reuse/resume request. The first nodemay establish a new session if there is no response to the secondrequest, or if a response to the second request does not include therequested session data. The owner core may not respond to the secondrequest, or may respond to the second request without the session data(or with incomplete session data). In some cases, the hash table mayinclude a status of the requested session, or information indicatingthat the session is invalid, expired or not resumable. In such asituation, the hash table may not respond, or may not respond with thesession data. The hash table and/or the owner node may provide aresponse indicating that the requested session is invalid, expired ornot resumable.

If the requested session is expired or no longer active, the receivingcore may attempt to establish (or resume) the session responsive to thesession resume/reuse request. The receiving core may create or assign anew session identifier, and may establish or resume the sessioncorresponding to the new session identifier, responsive to the sessionresume/reuse request. The receiving core may update the hash table withthe new session identifier. In certain embodiments, the receiving coremay install or initiate installation of the session at the owner core(e.g., as determined via the hash table). The receiving core may updatethe hash table via the hash table API, e.g., using a dht_put operationdiscussed above in connection with FIG. 9B.

If the requested session is invalid or not resumable, the receiving coremay establish a new session responsive to the session reuse/resumerequest. The receiving core may create or assign a new sessionidentifier, and may establish a new session corresponding to the newsession identifier, responsive to the session reuse/resume request. Thereceiving core may add the new session to the receiving core's cache. Inone embodiment, the receiving core may establish itself as an owner coreof the established session, e.g., by updating the hash table. Thereceiving core may update the hash table with the new session. Thereceiving core may install the new session and/or update the hash tablevia the hash table API, e.g., using the dht_put operation.

Referring to (911) and in further details, if the response includes thesession data, the receiving/first core may establish a (e.g., second)session cloned from the first session. The first node may establish thesecond session if a response to the second request includes therequested session data. The second session may comprise a session clonedfrom the first session. In some embodiments, the distributed or sharedhash table may provide a response or data comprising the session data,responsive to indexing using the key. The hash table may provide datacomprising the session data, responsive to a determination that therequested session is valid, unexpired, reusable, resumable and/oravailable at the owner core. In some embodiments, the owner core mayprovide or send at least a portion of the session data, e.g., responsiveto the second request. The hash table and/or owner core may provide aminimal set of data for cloning the session at the receiving core.

The receiving core of the receiving node may clone or make a copy of therequested session based on the session data. The receiving core mayestablish a session data structure consistent with the requestedsession, using the session data. The receiving core may establish thecloned session in or from a local cache of the receiving core. Forexample, the receiving core may establish, maintain and/or store a datastructure and/or settings of the second session in the local cache. Thecache may comprise memory of the receiving core. The receiving core mayestablish a protocol stack of the second session in the cache. Theestablished second session may be referred to as a cached session. Thelocale cache may not be accessible by another core and/or node. Thereceiving core or cached session may provide regular or heart beatsignals to the owner core or owner session, to indicate that the cachedsession has not aged-out, expired, or been deleted.

In some embodiments, responsive to establishment of the second session,the first node may store information about the second session in atleast one of the hash table (e.g., a local copy of the hash table)and/or the cache of the first node. In some embodiments, responsive tocompletion of session cloning, a client's certificate may be copied(e.g., to the second session and/or to the cache of the receiving core).The client's certificate may be copied in addition to session datastructure contents from the first session. In certain embodiments, somepointers holding an intermediate-CA certificate chain sent by the clientmay not be copied. In some cases, such pointers may not be valid on acore which does not own the session.

It should be noted that certain passages of this disclosure mayreference terms such as “first” and “second” in connection with nodes,requests, etc., for purposes of identifying or differentiating one fromanother or from others. These terms are not intended to merely relateentities (e.g., a first request and a second request) temporally oraccording to a sequence, although in some cases, these entities mayinclude such a relationship. Nor do these terms limit the number ofpossible entities (e.g., nodes) that may operate within a system orenvironment.

It should be understood that the systems described above may providemultiple ones of any or each of those components and these componentsmay be provided on either a standalone machine or, in some embodiments,on multiple machines in a distributed system. In addition, the systemsand methods described above may be provided as one or morecomputer-readable programs or executable instructions embodied on or inone or more articles of manufacture. The article of manufacture may be afloppy disk, a hard disk, a CD-ROM, a flash memory card, a PROM, a RAM,a ROM, or a magnetic tape. In general, the computer-readable programsmay be implemented in any programming language, such as LISP, PERL, C,C++, C#, PROLOG, or in any byte code language such as JAVA. The softwareprograms or executable instructions may be stored on or in one or morearticles of manufacture as object code.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdisclosed herein.

We claim:
 1. A method for managing one or more secure socket layer (SSL)sessions, the method comprising: (a) receiving, by a first core of afirst node from a cluster of nodes interconnected by a communicationback plane and intermediary between a client and a server, a firstrequest from the client to use a first session established with theserver, the first request comprising a session identifier of the firstsession; (b) determining, by the first core of the first node, that thefirst session is not identified in a cache of the first node; (c)identifying, by the first node via a hash table responsive to thedetermination, an owner node and owner core of the first session fromthe cluster of nodes using a key, the key determined based on thesession identifier, wherein the owner node comprises a second node ofthe plurality of nodes and the owner core comprises a second core on thesecond node; (d) sending via the communication back plane a secondrequest to the identified owner node and owner core for session data ofthe first session, the session data for establishing a second sessionwith the server; and (e) establishing, by the first core of the firstnode responsive to the first request, a new session if a response to thesecond request does not include the requested session data of the firstsession, or; (f) establishing, by the first core of the first noderesponsive to the first request, the second session as a copy of thefirst session if a response to the second request includes the requestedsession data of the first session.
 2. The method of claim 1, wherein (a)comprises receiving the first request to reuse, resume or clone thefirst session.
 3. The method of claim 1, wherein (a) comprises receivingthe first request from the client as part of a handshaking process forestablishing a SSL session with the server.
 4. The method of claim 1,wherein (b) comprises determining that the first session is notidentified in the cache based on the session identifier of the firstsession.
 5. The method of claim 1, wherein (b) comprises determiningthat the first node is not the owner node of the first session.
 6. Themethod of claim 1, wherein (c) comprises generating the key based on atleast one of the session identifier or a unique identifier of an entityfrom which the first request is received.
 7. The method of claim 1,further comprising receiving a response to the second request, theresponse indicating that the requested first session is invalid, expiredor not resumable.
 8. The method of claim 1, further comprisingestablishing, by the first node, the new session if there is no responseto the second request.
 9. The method of claim 1, further comprisingestablishing, by the first node, the second session comprising a sessioncloned from the first session using the requested session data.
 10. Themethod of claim 1, further comprising storing information about thesecond session in at least one of the hash table or the cache of thefirst node.
 11. A system for managing one or more secure socket layer(SSL) sessions, the system comprising: a cluster of nodes interconnectedby a communication back plane and intermediary between a client and aserver; and a first core of a first node from the cluster of nodes, thefirst core of the first node configured to: receive a first request fromthe client to use a first session established with the server, the firstrequest comprising a session identifier of the first session; determinewhether the first session is identified in a cache of the first node;identify, via a hash table responsive to the determination, an ownernode and owner core of the first session using a key, the key determinedbased on the session identifier; send a second request via thecommunication back plane to the identified owner node and owner core forsession data of the first session, the session data for establishing asecond session with the server, wherein the owner node comprises asecond node of the plurality of nodes and the owner core comprises asecond core on the second node; and wherein the first node is configuredto establish a new session responsive to the first request if theresponse to the second request does not include the requested sessiondata of the first session or establish the second session, responsive tothe first request, as a copy of the first session if a response to thesecond request includes the requested session data of the first session.12. The system of claim 11, wherein the first node is configured toreceive the first request, the first request to reuse, resume or clonethe first session.
 13. The system of claim 11, wherein the first node isconfigured to receive the first request from the client as part of ahandshaking process for establishing a SSL session with the server. 14.The system of claim 11, wherein the first node is configured todetermine whether the first session is identified in the cache based onthe session identifier of the first session.
 15. The system of claim 11,wherein the first node is configured to determine whether the first nodeis the owner node of the first session.
 16. The system of claim 11,wherein the first node is configured to generate the key based on atleast one of the session identifier or a unique identifier of an entityfrom which the first request is received.
 17. The system of claim 11,wherein the first node is configured to receive a response to the secondrequest, the response indicating that the requested first session isinvalid, expired or not resumable.
 18. The system of claim 11, whereinthe first node is configured to establish a new session if there is noresponse to the second request.
 19. The system of claim 11, wherein thefirst node is configured to establish the second session comprising asession cloned from the first session using the requested session data.20. The system of claim 11, wherein the first node is configured tostore information about the second session in at least one of the hashtable or the cache of the first node.